diff --git a/Makefile b/Makefile
index e2741491d..c0e30c10c 100644
--- a/Makefile
+++ b/Makefile
@@ -23,7 +23,7 @@ clean: pre-run
 pre-run:
 	@echo Make sure no previous build are in the folder
 
-	@rm -rf build/* actions client constants reducers selectors store utils types mattermost.client4* index.* mattermost.websocket_client*
+	@rm -rf build/* action_types actions client constants reducers selectors store utils types mattermost.client4* index.* mattermost.websocket_client*
 
 test: check-style
 	npm test
diff --git a/package-lock.json b/package-lock.json
index 47be7b58d..ab4d0fb6a 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1300,6 +1300,12 @@
         "@types/node": "*"
       }
     },
+    "@types/shallow-equals": {
+      "version": "1.0.0",
+      "resolved": "https://registry.npmjs.org/@types/shallow-equals/-/shallow-equals-1.0.0.tgz",
+      "integrity": "sha512-XtGSj7GYPfJwaklDtMEONj+kmpyCP8OLYoPqp/ROM8BL1VaF2IgYbxiEKfLvOyHN7c2d1KAFYzy6EIu8CSFt1A==",
+      "dev": true
+    },
     "@types/stack-utils": {
       "version": "1.0.1",
       "resolved": "https://registry.npmjs.org/@types/stack-utils/-/stack-utils-1.0.1.tgz",
@@ -6844,9 +6850,19 @@
       "dev": true
     },
     "serialize-error": {
-      "version": "2.1.0",
-      "resolved": "https://registry.npmjs.org/serialize-error/-/serialize-error-2.1.0.tgz",
-      "integrity": "sha1-ULZ51WNc34Rme9yOWa9OW4HV9go="
+      "version": "5.0.0",
+      "resolved": "https://registry.npmjs.org/serialize-error/-/serialize-error-5.0.0.tgz",
+      "integrity": "sha512-/VtpuyzYf82mHYTtI4QKtwHa79vAdU5OQpNPAmE/0UDdlGT0ZxHwC+J6gXkw29wwoVI8fMPsfcVHOwXtUQYYQA==",
+      "requires": {
+        "type-fest": "^0.8.0"
+      },
+      "dependencies": {
+        "type-fest": {
+          "version": "0.8.1",
+          "resolved": "https://registry.npmjs.org/type-fest/-/type-fest-0.8.1.tgz",
+          "integrity": "sha512-4dbzIzqvjtgiM5rw1k5rEHtBANKmdudhGyBEajN01fEyhaAIhsoKNy6y7+IN93IfpFtwY9iqi7kD+xwKhQsNJA=="
+        }
+      }
     },
     "serialize-javascript": {
       "version": "1.9.1",
diff --git a/package.json b/package.json
index 1f91a36e1..6049c0995 100644
--- a/package.json
+++ b/package.json
@@ -36,7 +36,7 @@
     "redux-thunk": "2.3.0",
     "remote-redux-devtools": "0.5.16",
     "reselect": "4.0.0",
-    "serialize-error": "2.1.0",
+    "serialize-error": "5.0.0",
     "shallow-equals": "1.0.0"
   },
   "husky": {
@@ -56,6 +56,7 @@
     "@babel/preset-env": "7.6.0",
     "@babel/preset-typescript": "7.6.0",
     "@babel/runtime": "7.6.0",
+    "@types/shallow-equals": "1.0.0",
     "@typescript-eslint/eslint-plugin": "2.3.1",
     "@typescript-eslint/parser": "2.3.1",
     "@types/jest": "24.0.18",
diff --git a/src/actions/bots.ts b/src/actions/bots.ts
index ec96b7a59..4254e6825 100644
--- a/src/actions/bots.ts
+++ b/src/actions/bots.ts
@@ -6,10 +6,11 @@ import {BotTypes} from 'action_types';
 import {bindClientFunc} from './helpers';
 
 import {ActionFunc} from 'types/actions';
+import {Bot, BotPatch} from 'types/bots';
 
 const BOTS_PER_PAGE_DEFAULT = 20;
 
-export function createBot(bot): ActionFunc {
+export function createBot(bot: Bot): ActionFunc {
     return bindClientFunc({
         clientFunc: Client4.createBot,
         onSuccess: BotTypes.RECEIVED_BOT_ACCOUNT,
@@ -19,7 +20,7 @@ export function createBot(bot): ActionFunc {
     });
 }
 
-export function patchBot(botUserId, botPatch): ActionFunc {
+export function patchBot(botUserId: string, botPatch: BotPatch): ActionFunc {
     return bindClientFunc({
         clientFunc: Client4.patchBot,
         onSuccess: BotTypes.RECEIVED_BOT_ACCOUNT,
@@ -30,7 +31,7 @@ export function patchBot(botUserId, botPatch): ActionFunc {
     });
 }
 
-export function loadBot(botUserId): ActionFunc {
+export function loadBot(botUserId: string): ActionFunc {
     return bindClientFunc({
         clientFunc: Client4.getBot,
         onSuccess: BotTypes.RECEIVED_BOT_ACCOUNT,
@@ -51,7 +52,7 @@ export function loadBots(page = 0, perPage = BOTS_PER_PAGE_DEFAULT): ActionFunc
     });
 }
 
-export function disableBot(botUserId): ActionFunc {
+export function disableBot(botUserId: string): ActionFunc {
     return bindClientFunc({
         clientFunc: Client4.disableBot,
         onSuccess: BotTypes.RECEIVED_BOT_ACCOUNT,
@@ -61,7 +62,7 @@ export function disableBot(botUserId): ActionFunc {
     });
 }
 
-export function enableBot(botUserId): ActionFunc {
+export function enableBot(botUserId: string): ActionFunc {
     return bindClientFunc({
         clientFunc: Client4.enableBot,
         onSuccess: BotTypes.RECEIVED_BOT_ACCOUNT,
@@ -71,7 +72,7 @@ export function enableBot(botUserId): ActionFunc {
     });
 }
 
-export function assignBot(botUserId, newOwnerId): ActionFunc {
+export function assignBot(botUserId: string, newOwnerId: string): ActionFunc {
     return bindClientFunc({
         clientFunc: Client4.assignBot,
         onSuccess: BotTypes.RECEIVED_BOT_ACCOUNT,
diff --git a/src/actions/channels.ts b/src/actions/channels.ts
index f956a2537..2babeaf43 100644
--- a/src/actions/channels.ts
+++ b/src/actions/channels.ts
@@ -573,7 +573,7 @@ export function getMyChannelMembers(teamId: string): ActionFunc {
 
 export function getChannelMembers(channelId: string, page = 0, perPage: number = General.CHANNELS_CHUNK_SIZE): ActionFunc {
     return async (dispatch: DispatchFunc, getState: GetStateFunc) => {
-        let channelMembers;
+        let channelMembers: ChannelMembership[];
 
         try {
             const channelMembersRequest = Client4.getChannelMembers(channelId, page, perPage);
diff --git a/src/actions/errors.ts b/src/actions/errors.ts
index 16b46b6c5..d5ba17dc5 100644
--- a/src/actions/errors.ts
+++ b/src/actions/errors.ts
@@ -1,7 +1,7 @@
 // Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
 // See LICENSE.txt for license information.
 import {ErrorTypes} from 'action_types';
-import serializeError from 'serialize-error';
+import {serializeError, ErrorObject} from 'serialize-error';
 import {Client4} from 'client';
 import EventEmitter from 'utils/event_emitter';
 import {DispatchFunc, ActionFunc} from 'types/actions';
@@ -22,7 +22,7 @@ export function dismissError(index: number): ActionFunc {
     };
 }
 
-export function getLogErrorAction(error: serializeError.ErrorObject, displayable = false) {
+export function getLogErrorAction(error: ErrorObject, displayable = false) {
     return {
         type: ErrorTypes.LOG_ERROR,
         displayable,
diff --git a/src/actions/files.ts b/src/actions/files.ts
index 8a04d97c9..53cf6fc8a 100644
--- a/src/actions/files.ts
+++ b/src/actions/files.ts
@@ -7,6 +7,7 @@ import {Action, batchActions, DispatchFunc, GetStateFunc, ActionFunc} from 'type
 
 import {logError} from './errors';
 import {bindClientFunc, forceLogoutIfNecessary} from './helpers';
+import {FileUploadResponse} from 'types/files';
 
 export function getFilesForPost(postId: string): ActionFunc {
     return async (dispatch: DispatchFunc, getState: GetStateFunc) => {
@@ -34,7 +35,7 @@ export function uploadFile(channelId: string, rootId: string, clientIds: Array<s
     return async (dispatch: DispatchFunc, getState: GetStateFunc) => {
         dispatch({type: FileTypes.UPLOAD_FILES_REQUEST, data: {}}, getState);
 
-        let files;
+        let files: FileUploadResponse;
         try {
             files = await Client4.uploadFile(fileFormData, formBoundary);
         } catch (error) {
diff --git a/src/actions/gifs.ts b/src/actions/gifs.ts
index 5b9fcc246..d7070ab89 100644
--- a/src/actions/gifs.ts
+++ b/src/actions/gifs.ts
@@ -3,63 +3,64 @@
 import {GifTypes} from 'action_types';
 import {Client4} from 'client';
 import gfycatSdk from 'utils/gfycat_sdk';
-import {ActionResult, DispatchFunc, GetStateFunc} from 'types/actions';
+import {DispatchFunc, GetStateFunc} from 'types/actions';
+import {GlobalState} from 'types/store';
 
 // APP PROPS
 
-export function saveAppPropsRequest(props) {
+export function saveAppPropsRequest(props: any) {
     return {
         type: GifTypes.SAVE_APP_PROPS,
         props,
     };
 }
 
-export function saveAppProps(appProps) {
+export function saveAppProps(appProps: any) {
     return (dispatch: DispatchFunc, getState: GetStateFunc) => {
         const {GfycatApiKey, GfycatApiSecret} = getState().entities.general.config;
-        gfycatSdk(GfycatApiKey, GfycatApiSecret).authenticate();
+        gfycatSdk(GfycatApiKey!, GfycatApiSecret!).authenticate();
         dispatch(saveAppPropsRequest(appProps));
     };
 }
 
 // SEARCH
 
-export function selectSearchText(searchText) {
+export function selectSearchText(searchText: string) {
     return {
         type: GifTypes.SELECT_SEARCH_TEXT,
         searchText,
     };
 }
 
-export function updateSearchText(searchText) {
+export function updateSearchText(searchText: string) {
     return {
         type: GifTypes.UPDATE_SEARCH_TEXT,
         searchText,
     };
 }
 
-export function searchBarTextSave(searchBarText) {
+export function searchBarTextSave(searchBarText: string) {
     return {
         type: GifTypes.SAVE_SEARCH_BAR_TEXT,
         searchBarText,
     };
 }
 
-export function invalidateSearchText(searchText) {
+export function invalidateSearchText(searchText: string) {
     return {
         type: GifTypes.INVALIDATE_SEARCH_TEXT,
         searchText,
     };
 }
 
-export function requestSearch(searchText) {
+export function requestSearch(searchText: string) {
     return {
         type: GifTypes.REQUEST_SEARCH,
         searchText,
     };
 }
 
-export function receiveSearch({searchText, count, start, json}) {
+export function receiveSearch({searchText, count, start, json}: {searchText: string; count: number; start: number; json: any}) {
     return {
         type: GifTypes.RECEIVE_SEARCH,
         searchText,
@@ -71,14 +72,14 @@ export function receiveSearch({searchText, count, start, json}) {
     };
 }
 
-export function receiveSearchEnd(searchText) {
+export function receiveSearchEnd(searchText: string) {
     return {
         type: GifTypes.RECEIVE_SEARCH_END,
         searchText,
     };
 }
 
-export function errorSearching(err, searchText) {
+export function errorSearching(err: any, searchText: string) {
     return {
         type: GifTypes.SEARCH_FAILURE,
         searchText,
@@ -86,7 +87,7 @@ export function errorSearching(err, searchText) {
     };
 }
 
-export function receiveCategorySearch({tagName, json}) {
+export function receiveCategorySearch({tagName, json}: {tagName: string; json: any}) {
     return {
         type: GifTypes.RECEIVE_CATEGORY_SEARCH,
         searchText: tagName,
@@ -101,7 +102,7 @@ export function clearSearchResults() {
     };
 }
 
-export function requestSearchById(gfyId) {
+export function requestSearchById(gfyId: string) {
     return {
         type: GifTypes.SEARCH_BY_ID_REQUEST,
         payload: {
@@ -110,7 +111,7 @@ export function requestSearchById(gfyId) {
     };
 }
 
-export function receiveSearchById(gfyId, gfyItem) {
+export function receiveSearchById(gfyId: string, gfyItem: any) {
     return {
         type: GifTypes.SEARCH_BY_ID_SUCCESS,
         payload: {
@@ -120,7 +121,7 @@ export function receiveSearchById(gfyId, gfyItem) {
     };
 }
 
-export function errorSearchById(err, gfyId) {
+export function errorSearchById(err: any, gfyId: string) {
     return {
         type: GifTypes.SEARCH_BY_ID_FAILURE,
         err,
@@ -128,21 +129,21 @@ export function errorSearchById(err, gfyId) {
     };
 }
 
-export function searchScrollPosition(scrollPosition) {
+export function searchScrollPosition(scrollPosition: number) {
     return {
         type: GifTypes.SAVE_SEARCH_SCROLL_POSITION,
         scrollPosition,
     };
 }
 
-export function searchPriorLocation(priorLocation) {
+export function searchPriorLocation(priorLocation: number) {
     return {
         type: GifTypes.SAVE_SEARCH_PRIOR_LOCATION,
         priorLocation,
     };
 }
 
-export function searchGfycat({searchText, count = 30, startIndex = 0}) {
+export function searchGfycat({searchText, count = 30, startIndex = 0}: { searchText: string; count?: number; startIndex?: number}) {
     let start = startIndex;
     return (dispatch: DispatchFunc, getState: GetStateFunc) => {
         const {GfycatApiKey, GfycatApiSecret} = getState().entities.general.config;
@@ -151,8 +152,9 @@ export function searchGfycat({searchText, count = 30, startIndex = 0}) {
             start = resultsByTerm[searchText].start + count;
         }
         dispatch(requestSearch(searchText));
-        gfycatSdk(GfycatApiKey, GfycatApiSecret).authenticate();
-        return gfycatSdk(GfycatApiKey, GfycatApiSecret).search({search_text: searchText, count, start}).then((json) => {
+        const sdk = gfycatSdk(GfycatApiKey!, GfycatApiSecret!);
+        sdk.authenticate();
+        return sdk.search({search_text: searchText, count, start}).then((json: any) => {
             if (json.errorMessage) {
                 // There was no results before
                 if (resultsByTerm[searchText].items) {
@@ -175,7 +177,7 @@ export function searchGfycat({searchText, count = 30, startIndex = 0}) {
                 );
             }
         }).catch(
-            (err) => dispatch(errorSearching(err, searchText))
+            (err: any) => dispatch(errorSearching(err, searchText))
         );
     };
 }
@@ -189,8 +191,8 @@ export function searchCategory({tagName = '', gfyCount = 30, cursorPos = undefin
             cursor = resultsByTerm[tagName].cursor;
         }
         dispatch(requestSearch(tagName));
-        return gfycatSdk(GfycatApiKey, GfycatApiSecret).getTrendingCategories({tagName, gfyCount, cursor}).then(
-            (json) => {
+        return gfycatSdk(GfycatApiKey!, GfycatApiSecret!).getTrendingCategories({tagName, gfyCount, cursor}).then(
+            (json: any) => {
                 if (json.errorMessage) {
                     if (resultsByTerm[tagName].gfycats) {
                         dispatch(receiveSearchEnd(tagName));
@@ -214,12 +216,12 @@ export function searchCategory({tagName = '', gfyCount = 30, cursorPos = undefin
                     }
                 }
             }
-        ).catch((err) => dispatch(errorSearching(err, tagName)));
+        ).catch((err: any) => dispatch(errorSearching(err, tagName)));
     };
 }
 
-export function shouldSearch(state, searchText) {
-    const resultsByTerm = state.search.resultsByTerm[searchText];
+export function shouldSearch(state: GlobalState, searchText: string) {
+    const resultsByTerm = state.entities.gifs.search.resultsByTerm[searchText];
     if (!resultsByTerm) {
         return true;
     } else if (resultsByTerm.isFetching) {
@@ -230,7 +232,7 @@ export function shouldSearch(state, searchText) {
     return resultsByTerm.didInvalidate;
 }
 
-export function searchIfNeeded(searchText) {
+export function searchIfNeeded(searchText: string) {
     return (dispatch: DispatchFunc, getState: GetStateFunc) => {
         if (shouldSearch(getState(), searchText)) {
             if (searchText.toLowerCase() === 'trending') {
@@ -242,7 +244,7 @@ export function searchIfNeeded(searchText) {
     };
 }
 
-export function searchIfNeededInitial(searchText) {
+export function searchIfNeededInitial(searchText: string) {
     return (dispatch: DispatchFunc, getState: GetStateFunc) => {
         dispatch(updateSearchText(searchText));
         if (shouldSearchInitial(getState(), searchText)) {
@@ -255,7 +257,7 @@ export function searchIfNeededInitial(searchText) {
     };
 }
 
-export function shouldSearchInitial(state, searchText) {
+export function shouldSearchInitial(state: GlobalState, searchText: string) {
     const resultsByTerm = state.entities.gifs.search.resultsByTerm[searchText];
     if (!resultsByTerm) {
         return true;
@@ -266,24 +268,24 @@ export function shouldSearchInitial(state, searchText) {
     return false;
 }
 
-export function searchById(gfyId) {
+export function searchById(gfyId: string) {
     return (dispatch: DispatchFunc, getState: GetStateFunc) => {
         const {GfycatApiKey, GfycatApiSecret} = getState().entities.general.config;
         dispatch(requestSearchById(gfyId));
-        return gfycatSdk(GfycatApiKey, GfycatApiSecret).searchById({id: gfyId}).then(
-            (response) => {
+        return gfycatSdk(GfycatApiKey!, GfycatApiSecret!).searchById({id: gfyId}).then(
+            (response: any) => {
                 dispatch(receiveSearchById(gfyId, response.gfyItem));
                 dispatch(cacheGifsRequest([response.gfyItem]));
             }
-        ).catch((err) => dispatch(errorSearchById(err, gfyId)));
+        ).catch((err: any) => dispatch(errorSearchById(err, gfyId)));
     };
 }
 
-export function shouldSearchById(state, gfyId) {
+export function shouldSearchById(state: GlobalState, gfyId: string) {
     return !state.entities.gifs.cache.gifs[gfyId]; //TODO investigate, used to be !state.cache.gifs[gfyId];
 }
 
-export function searchByIdIfNeeded(gfyId) {
+export function searchByIdIfNeeded(gfyId: string) {
     return (dispatch: DispatchFunc, getState: GetStateFunc) => {
         if (shouldSearchById(getState(), gfyId)) {
             return dispatch(searchById(gfyId));
@@ -293,25 +295,25 @@ export function searchByIdIfNeeded(gfyId) {
     };
 }
 
-export function saveSearchScrollPosition(scrollPosition) {
+export function saveSearchScrollPosition(scrollPosition: number) {
     return (dispatch: DispatchFunc) => {
         dispatch(searchScrollPosition(scrollPosition));
     };
 }
 
-export function saveSearchPriorLocation(priorLocation) {
+export function saveSearchPriorLocation(priorLocation: number) {
     return (dispatch: DispatchFunc) => {
         dispatch(searchPriorLocation(priorLocation));
     };
 }
 
-export function searchTextUpdate(searchText) {
+export function searchTextUpdate(searchText: string) {
     return (dispatch: DispatchFunc) => {
         dispatch(updateSearchText(searchText));
     };
 }
 
-export function saveSearchBarText(searchBarText) {
+export function saveSearchBarText(searchBarText: string) {
     return (dispatch: DispatchFunc) => {
         dispatch(searchBarTextSave(searchBarText));
     };
@@ -325,14 +327,14 @@ export function categoriesListRequest() {
     };
 }
 
-export function categoriesListReceived(json) {
+export function categoriesListReceived(json: any) {
     return {
         type: GifTypes.CATEGORIES_LIST_RECEIVED,
         ...json,
     };
 }
 
-export function categoriesListFailure(err) {
+export function categoriesListFailure(err: any) {
     return {
         type: GifTypes.CATEGORIES_LIST_FAILURE,
         err,
@@ -352,8 +354,8 @@ export function requestCategoriesList({count = 60} = {}) {
             ...(count && {count}),
             ...(cursor && {cursor}),
         };
-        return gfycatSdk(GfycatApiKey, GfycatApiSecret).getCategories(options).then((json) => {
-            const newGfycats = json.tags.reduce((gfycats, tag) => {
+        return gfycatSdk(GfycatApiKey!, GfycatApiSecret!).getCategories(options).then((json: any) => {
+            const newGfycats = json.tags.reduce((gfycats: any[], tag: any) => {
                 if (tag.gfycats[0] && tag.gfycats[0].width) {
                     return [...gfycats, ...tag.gfycats];
                 }
@@ -362,7 +364,7 @@ export function requestCategoriesList({count = 60} = {}) {
             dispatch(cacheGifsRequest(newGfycats));
             dispatch(categoriesListReceived(json));
         }).catch(
-            (err) => {
+            (err: any) => {
                 dispatch(categoriesListFailure(err));
             }
         );
@@ -381,7 +383,7 @@ export function requestCategoriesListIfNeeded({
     };
 }
 
-export function shouldRequestCategoriesList(state) {
+export function shouldRequestCategoriesList(state: {hasMore: boolean; isFetching: boolean; tagsList: any[]}) {
     const {hasMore, isFetching, tagsList} = state;
     if (!tagsList || !tagsList.length) {
         return true;
@@ -404,14 +406,14 @@ export function cacheRequest() {
     };
 }
 
-export function cacheGifs(gifs) {
+export function cacheGifs(gifs: any) {
     return {
         type: GifTypes.CACHE_GIFS,
         gifs,
     };
 }
 
-export function cacheGifsRequest(gifs) {
+export function cacheGifsRequest(gifs: any) {
     return async (dispatch: DispatchFunc, getState: GetStateFunc) => {
         dispatch(cacheRequest());
         dispatch(cacheGifs(gifs));
diff --git a/src/actions/groups.ts b/src/actions/groups.ts
index 8e9e3a6ca..20f72f0da 100644
--- a/src/actions/groups.ts
+++ b/src/actions/groups.ts
@@ -27,7 +27,7 @@ export function linkGroupSyncable(groupID: string, syncableID: string, syncableT
 
         const dispatches: Action[] = [];
 
-        let type;
+        let type = '';
         switch (syncableType) {
         case Groups.SYNCABLE_TYPE_TEAM:
             dispatches.push({type: GroupTypes.RECEIVED_GROUPS_ASSOCIATED_TO_TEAM, data: {teamID: syncableID, groups: [{id: groupID}]}});
@@ -65,7 +65,7 @@ export function unlinkGroupSyncable(groupID: string, syncableID: string, syncabl
 
         const dispatches: Action[] = [];
 
-        let type;
+        let type = '';
         const data = {group_id: groupID, syncable_id: syncableID};
         switch (syncableType) {
         case Groups.SYNCABLE_TYPE_TEAM:
@@ -105,7 +105,7 @@ export function getGroupSyncables(groupID: string, syncableType: SyncableType):
             return {error};
         }
 
-        let type;
+        let type = '';
         switch (syncableType) {
         case Groups.SYNCABLE_TYPE_TEAM:
             type = GroupTypes.RECEIVED_GROUP_TEAMS;
diff --git a/src/actions/helpers.ts b/src/actions/helpers.ts
index 9c598829e..c3a74c6ad 100644
--- a/src/actions/helpers.ts
+++ b/src/actions/helpers.ts
@@ -68,7 +68,7 @@ export function bindClientFunc({
     onFailure,
     params = [],
 }: {
-    clientFunc: (...args) => Promise<any>;
+    clientFunc: (...args: any[]) => Promise<any>;
     onRequest?: ActionType;
     onSuccess?: ActionType | Array<ActionType>;
     onFailure?: ActionType;
@@ -79,7 +79,7 @@ export function bindClientFunc({
             dispatch(requestData(onRequest), getState);
         }
 
-        let data = null;
+        let data: any = null;
         try {
             data = await clientFunc(...params);
         } catch (error) {
@@ -107,7 +107,7 @@ export function bindClientFunc({
 // Debounce function based on underscores modified to use es6 and a cb
 
 export function debounce(func: (...args: any) => unknown, wait: number, immediate: boolean, cb: () => unknown) {
-    let timeout;
+    let timeout: NodeJS.Timeout|null;
     return function fx(...args: Array<any>) {
         const runLater = () => {
             timeout = null;
diff --git a/src/actions/plugins.ts b/src/actions/plugins.ts
index 7380a23cd..1951e9bc6 100644
--- a/src/actions/plugins.ts
+++ b/src/actions/plugins.ts
@@ -8,7 +8,14 @@ import {PluginTypes} from 'action_types';
 
 import {ActionFunc} from 'types/actions';
 
-export function getMarketplacePlugins(filter): ActionFunc {
+export type MarketplacePluginFilter = {
+    Page: number;
+    PerPage: number;
+    Filter: string;
+    ServerVersion: string;
+}
+
+export function getMarketplacePlugins(filter: MarketplacePluginFilter): ActionFunc {
     return bindClientFunc({
         clientFunc: Client4.getMarketplacePlugins,
         onSuccess: PluginTypes.RECEIVED_MARKETPLACE_PLUGINS,
diff --git a/src/actions/posts.ts b/src/actions/posts.ts
index d0484d7de..bf3643b38 100644
--- a/src/actions/posts.ts
+++ b/src/actions/posts.ts
@@ -27,13 +27,18 @@ import {
     savePreferences,
 } from './preferences';
 import {getProfilesByIds, getProfilesByUsernames, getStatusesByIds} from './users';
-import {Action, ActionFunc, ActionResult, batchActions, DispatchFunc, GetStateFunc} from 'types/actions';
+import {Action, ActionFunc, ActionResult, batchActions, DispatchFunc, GetStateFunc, GenericAction} from 'types/actions';
 import {GlobalState} from 'types/store';
 import {Post} from 'types/posts';
+import {Error} from 'types/errors';
+import {Reaction} from 'types/reactions';
+import {UserProfile} from 'types/users';
+import {Dictionary} from 'types/utilities';
+import {CustomEmoji} from 'types/emojis';
 
 // receivedPost should be dispatched after a single post from the server. This typically happens when an existing post
 // is updated.
-export function receivedPost(post) {
+export function receivedPost(post: Post) {
     return {
         type: PostTypes.RECEIVED_POST,
         data: post,
@@ -42,7 +47,7 @@ export function receivedPost(post) {
 
 // receivedNewPost should be dispatched when receiving a newly created post or when sending a request to the server
 // to make a new post.
-export function receivedNewPost(post) {
+export function receivedNewPost(post: Post) {
     return {
         type: PostTypes.RECEIVED_NEW_POST,
         data: post,
@@ -51,7 +56,7 @@ export function receivedNewPost(post) {
 
 // receivedPosts should be dispatched when receiving multiple posts from the server that may or may not be ordered.
 // This will typically be used alongside other actions like receivedPostsAfter which require the posts to be ordered.
-export function receivedPosts(posts) {
+export function receivedPosts(posts: CombinedPostList) {
     return {
         type: PostTypes.RECEIVED_POSTS,
         data: posts,
@@ -59,7 +64,7 @@ export function receivedPosts(posts) {
 }
 
 // receivedPostsAfter should be dispatched when receiving an ordered list of posts that come before a given post.
-export function receivedPostsAfter(posts, channelId, afterPostId, recent = false) {
+export function receivedPostsAfter(posts: Array<Post>, channelId: string, afterPostId: string, recent = false) {
     return {
         type: PostTypes.RECEIVED_POSTS_AFTER,
         channelId,
@@ -70,7 +75,7 @@ export function receivedPostsAfter(posts, channelId, afterPostId, recent = false
 }
 
 // receivedPostsBefore should be dispatched when receiving an ordered list of posts that come after a given post.
-export function receivedPostsBefore(posts, channelId, beforePostId, oldest = false) {
+export function receivedPostsBefore(posts: Array<Post>, channelId: string, beforePostId: string, oldest = false) {
     return {
         type: PostTypes.RECEIVED_POSTS_BEFORE,
         channelId,
@@ -83,7 +88,7 @@ export function receivedPostsBefore(posts, channelId, beforePostId, oldest = fal
 // receivedPostsSince should be dispatched when receiving a list of posts that have been updated since a certain time.
 // Due to how the API endpoint works, some of these posts will be ordered, but others will not, so this needs special
 // handling from the reducers.
-export function receivedPostsSince(posts, channelId) {
+export function receivedPostsSince(posts: Array<Post>, channelId: string) {
     return {
         type: PostTypes.RECEIVED_POSTS_SINCE,
         channelId,
@@ -93,7 +98,7 @@ export function receivedPostsSince(posts, channelId) {
 
 // receivedPostsInChannel should be dispatched when receiving a list of ordered posts within a channel when the
 // the adjacent posts are not known.
-export function receivedPostsInChannel(posts, channelId, recent = false, oldest = false) {
+export function receivedPostsInChannel(posts: CombinedPostList, channelId: string, recent = false, oldest = false) {
     return {
         type: PostTypes.RECEIVED_POSTS_IN_CHANNEL,
         channelId,
@@ -104,7 +109,7 @@ export function receivedPostsInChannel(posts, channelId, recent = false, oldest
 }
 
 // receivedPostsInThread should be dispatched when receiving a list of unordered posts in a thread.
-export function receivedPostsInThread(posts, rootId) {
+export function receivedPostsInThread(posts: Array<Post>, rootId: string) {
     return {
         type: PostTypes.RECEIVED_POSTS_IN_THREAD,
         data: posts,
@@ -114,7 +119,7 @@ export function receivedPostsInThread(posts, rootId) {
 
 // postDeleted should be dispatched when a post has been deleted and should be replaced with a "message deleted"
 // placeholder. This typically happens when a post is deleted by another user.
-export function postDeleted(post) {
+export function postDeleted(post: Post) {
     return {
         type: PostTypes.POST_DELETED,
         data: post,
@@ -123,14 +128,14 @@ export function postDeleted(post) {
 
 // postRemoved should be dispatched when a post should be immediately removed. This typically happens when a post is
 // deleted by the current user.
-export function postRemoved(post) {
+export function postRemoved(post: Post) {
     return {
         type: PostTypes.POST_REMOVED,
         data: post,
     };
 }
 
-export function getPost(postId) {
+export function getPost(postId: string) {
     return async (dispatch: DispatchFunc, getState: GetStateFunc) => {
         let post;
 
@@ -157,7 +162,7 @@ export function getPost(postId) {
     };
 }
 
-export function createPost(post, files: any[] = []) {
+export function createPost(post: Post, files: any[] = []) {
     return async (dispatch: DispatchFunc, getState: GetStateFunc) => {
         const state = getState();
         const currentUserId = state.entities.users.currentUserId;
@@ -205,7 +210,7 @@ export function createPost(post, files: any[] = []) {
             meta: {
                 offline: {
                     effect: () => Client4.createPost({...newPost, create_at: 0}),
-                    commit: (success, payload) => {
+                    commit: (result: any, payload: any) => {
                         const actions: Action[] = [
                             receivedPost(payload),
                             {
@@ -239,7 +244,7 @@ export function createPost(post, files: any[] = []) {
                     },
                     maxRetry: 0,
                     offlineRollback: true,
-                    rollback: (success, error) => {
+                    rollback: (result: any, error: Error) => {
                         const data = {
                             ...newPost,
                             id: pendingPostId,
@@ -354,11 +359,11 @@ export function resetCreatePostRequest() {
     return {type: PostTypes.CREATE_POST_RESET_REQUEST};
 }
 
-export function deletePost(post) {
+export function deletePost(post: ExtendedPost) {
     return (dispatch: DispatchFunc, getState: GetStateFunc) => {
         const state = getState();
         const delPost = {...post};
-        if (delPost.type === Posts.POST_TYPES.COMBINED_USER_ACTIVITY) {
+        if (delPost.type === Posts.POST_TYPES.COMBINED_USER_ACTIVITY && delPost.system_post_ids) {
             delPost.system_post_ids.forEach((systemPostId) => {
                 const systemPost = Selectors.getPost(state, systemPostId);
                 if (systemPost) {
@@ -383,7 +388,7 @@ export function deletePost(post) {
     };
 }
 
-export function editPost(post) {
+export function editPost(post: Post) {
     return bindClientFunc({
         clientFunc: Client4.patchPost,
         onRequest: PostTypes.EDIT_POST_REQUEST,
@@ -395,7 +400,7 @@ export function editPost(post) {
     });
 }
 
-export function pinPost(postId) {
+export function pinPost(postId: string) {
     return async (dispatch: DispatchFunc, getState: GetStateFunc) => {
         dispatch({type: PostTypes.EDIT_POST_REQUEST}, getState);
         let posts;
@@ -432,7 +437,7 @@ export function pinPost(postId) {
     };
 }
 
-export function unpinPost(postId) {
+export function unpinPost(postId: string) {
     return async (dispatch: DispatchFunc, getState: GetStateFunc) => {
         dispatch({type: PostTypes.EDIT_POST_REQUEST}, getState);
         let posts;
@@ -469,7 +474,7 @@ export function unpinPost(postId) {
     };
 }
 
-export function addReaction(postId, emojiName) {
+export function addReaction(postId: string, emojiName: string) {
     return async (dispatch: DispatchFunc, getState: GetStateFunc) => {
         const currentUserId = getState().entities.users.currentUserId;
 
@@ -491,7 +496,7 @@ export function addReaction(postId, emojiName) {
     };
 }
 
-export function removeReaction(postId, emojiName) {
+export function removeReaction(postId: string, emojiName: string) {
     return async (dispatch: DispatchFunc, getState: GetStateFunc) => {
         const currentUserId = getState().entities.users.currentUserId;
 
@@ -512,7 +517,7 @@ export function removeReaction(postId, emojiName) {
     };
 }
 
-export function getCustomEmojiForReaction(name) {
+export function getCustomEmojiForReaction(name: string) {
     return async (dispatch: DispatchFunc, getState: GetStateFunc) => {
         const nonExistentEmoji = getState().entities.emojis.nonExistentEmoji;
         const customEmojisByName = selectCustomEmojisByName(getState());
@@ -533,7 +538,7 @@ export function getCustomEmojiForReaction(name) {
     };
 }
 
-export function getReactionsForPost(postId) {
+export function getReactionsForPost(postId: string) {
     return async (dispatch: DispatchFunc, getState: GetStateFunc) => {
         let reactions;
         try {
@@ -549,7 +554,7 @@ export function getReactionsForPost(postId) {
             const customEmojisByName = selectCustomEmojisByName(getState());
             const emojisToLoad = new Set<string>();
 
-            reactions.forEach((r) => {
+            reactions.forEach((r: Reaction) => {
                 const name = r.emoji_name;
 
                 if (systemEmojis.has(name)) {
@@ -585,7 +590,7 @@ export function getReactionsForPost(postId) {
     };
 }
 
-export function flagPost(postId) {
+export function flagPost(postId: string) {
     return async (dispatch: DispatchFunc, getState: GetStateFunc) => {
         const {currentUserId} = getState().entities.users;
         const preference = {
@@ -601,7 +606,7 @@ export function flagPost(postId) {
     };
 }
 
-export function getPostThread(rootId, fetchThreads = true) {
+export function getPostThread(rootId: string, fetchThreads = true) {
     return async (dispatch: DispatchFunc, getState: GetStateFunc) => {
         dispatch({type: PostTypes.GET_POST_THREAD_REQUEST}, getState);
 
@@ -630,7 +635,7 @@ export function getPostThread(rootId, fetchThreads = true) {
     };
 }
 
-export function getPosts(channelId, page = 0, perPage = Posts.POST_CHUNK_SIZE, fetchThreads = true) {
+export function getPosts(channelId: string, page = 0, perPage = Posts.POST_CHUNK_SIZE, fetchThreads = true) {
     return async (dispatch: DispatchFunc, getState: GetStateFunc) => {
         let posts;
 
@@ -652,7 +657,7 @@ export function getPosts(channelId, page = 0, perPage = Posts.POST_CHUNK_SIZE, f
     };
 }
 
-export function getPostsUnread(channelId, fetchThreads = true) {
+export function getPostsUnread(channelId: string, fetchThreads = true) {
     return async (dispatch: DispatchFunc, getState: GetStateFunc) => {
         const userId = getCurrentUserId(getState());
         let posts;
@@ -679,7 +684,7 @@ export function getPostsUnread(channelId, fetchThreads = true) {
     };
 }
 
-export function getPostsSince(channelId, since, fetchThreads = true) {
+export function getPostsSince(channelId: string, since: number, fetchThreads = true) {
     return async (dispatch: DispatchFunc, getState: GetStateFunc) => {
         let posts;
         try {
@@ -703,7 +708,7 @@ export function getPostsSince(channelId, since, fetchThreads = true) {
     };
 }
 
-export function getPostsBefore(channelId, postId, page = 0, perPage = Posts.POST_CHUNK_SIZE, fetchThreads = true) {
+export function getPostsBefore(channelId: string, postId: string, page = 0, perPage = Posts.POST_CHUNK_SIZE, fetchThreads = true) {
     return async (dispatch: DispatchFunc, getState: GetStateFunc) => {
         let posts;
         try {
@@ -724,7 +729,7 @@ export function getPostsBefore(channelId, postId, page = 0, perPage = Posts.POST
     };
 }
 
-export function getPostsAfter(channelId, postId, page = 0, perPage = Posts.POST_CHUNK_SIZE, fetchThreads = true) {
+export function getPostsAfter(channelId: string, postId: string, page = 0, perPage = Posts.POST_CHUNK_SIZE, fetchThreads = true) {
     return async (dispatch: DispatchFunc, getState: GetStateFunc) => {
         let posts;
         try {
@@ -744,8 +749,14 @@ export function getPostsAfter(channelId, postId, page = 0, perPage = Posts.POST_
         return {data: posts};
     };
 }
+export type CombinedPostList = {
+    posts: Array<Post>;
+    order: Array<string>;
+    next_post_id: string;
+    prev_post_id: string;
+}
 
-export function getPostsAround(channelId, postId, perPage = Posts.POST_CHUNK_SIZE / 2, fetchThreads = true) {
+export function getPostsAround(channelId: string, postId: string, perPage = Posts.POST_CHUNK_SIZE / 2, fetchThreads = true) {
     return async (dispatch: DispatchFunc, getState: GetStateFunc) => {
         let after;
         let thread;
@@ -764,7 +775,7 @@ export function getPostsAround(channelId, postId, perPage = Posts.POST_CHUNK_SIZ
         }
 
         // Dispatch a combined post list so that the order is correct for postsInChannel
-        const posts = {
+        const posts: CombinedPostList = {
             posts: {
                 ...after.posts,
                 ...thread.posts,
@@ -792,7 +803,7 @@ export function getPostsAround(channelId, postId, perPage = Posts.POST_CHUNK_SIZ
 
 // getThreadsForPosts is intended for an array of posts that have been batched
 // (see the actions/websocket_actions/handleNewPostEvents function in the webapp)
-export function getThreadsForPosts(posts, fetchThreads = true) {
+export function getThreadsForPosts(posts: Array<Post>, fetchThreads = true) {
     return (dispatch: DispatchFunc, getState: GetStateFunc) => {
         if (!Array.isArray(posts) || !posts.length) {
             return {data: true};
@@ -878,8 +889,8 @@ export function getProfilesAndStatusesForPosts(postsArrayOrMap: Array<Post>|Map<
     return Promise.all(promises);
 }
 
-export function getNeededAtMentionedUsernames(state, posts): Set<string> {
-    let usersByUsername; // Populate this lazily since it's relatively expensive
+export function getNeededAtMentionedUsernames(state: GlobalState, posts: Array<Post>): Set<string> {
+    let usersByUsername: Dictionary<UserProfile>; // Populate this lazily since it's relatively expensive
 
     const usernamesToLoad = new Set<string>();
 
@@ -916,12 +927,12 @@ export function getNeededAtMentionedUsernames(state, posts): Set<string> {
     return usernamesToLoad;
 }
 
-function buildPostAttachmentText(attachments) {
+function buildPostAttachmentText(attachments: Array<any>) {
     let attachmentText = '';
 
     attachments.forEach((a) => {
         if (a.fields && a.fields.length) {
-            a.fields.forEach((f) => {
+            a.fields.forEach((f: any) => {
                 attachmentText += ' ' + (f.value || '');
             });
         }
@@ -938,7 +949,7 @@ function buildPostAttachmentText(attachments) {
     return attachmentText;
 }
 
-export function getNeededCustomEmojis(state: GlobalState, posts): Set<string> {
+export function getNeededCustomEmojis(state: GlobalState, posts: Array<Post>): Set<string> {
     if (getConfig(state).EnableCustomEmoji !== 'true') {
         return new Set<string>();
     }
@@ -950,7 +961,7 @@ export function getNeededCustomEmojis(state: GlobalState, posts): Set<string> {
 
     let customEmojisToLoad = new Set<string>();
 
-    let customEmojisByName; // Populate this lazily since it's relatively expensive
+    let customEmojisByName: Map<string, CustomEmoji>; // Populate this lazily since it's relatively expensive
     const nonExistentEmoji = state.entities.emojis.nonExistentEmoji;
 
     posts.forEach((post) => {
@@ -986,17 +997,18 @@ export function getNeededCustomEmojis(state: GlobalState, posts): Set<string> {
 
     return customEmojisToLoad;
 }
+export type ExtendedPost = Post & { system_post_ids?: string[] };
 
-export function removePost(post) {
+export function removePost(post: ExtendedPost) {
     return (dispatch: DispatchFunc, getState: GetStateFunc) => {
-        if (post.type === Posts.POST_TYPES.COMBINED_USER_ACTIVITY) {
+        if (post.type === Posts.POST_TYPES.COMBINED_USER_ACTIVITY && post.system_post_ids) {
             const state = getState();
 
             for (const systemPostId of post.system_post_ids) {
                 const systemPost = Selectors.getPost(state, systemPostId);
 
                 if (systemPost) {
-                    dispatch(removePost(systemPost) as any);
+                    dispatch(removePost(systemPost as any) as any);
                 }
             }
         } else {
@@ -1005,7 +1017,7 @@ export function removePost(post) {
     };
 }
 
-export function selectPost(postId) {
+export function selectPost(postId: string) {
     return async (dispatch: DispatchFunc, getState: GetStateFunc) => {
         dispatch({
             type: PostTypes.RECEIVED_POST_SELECTED,
@@ -1016,14 +1028,14 @@ export function selectPost(postId) {
     };
 }
 
-export function selectFocusedPostId(postId) {
+export function selectFocusedPostId(postId: string) {
     return {
         type: PostTypes.RECEIVED_FOCUSED_POST,
         data: postId,
     };
 }
 
-export function unflagPost(postId) {
+export function unflagPost(postId: string) {
     return async (dispatch: DispatchFunc, getState: GetStateFunc) => {
         const {currentUserId} = getState().entities.users;
         const preference = {
@@ -1038,7 +1050,7 @@ export function unflagPost(postId) {
     };
 }
 
-export function getOpenGraphMetadata(url) {
+export function getOpenGraphMetadata(url: string) {
     return async (dispatch: DispatchFunc, getState: GetStateFunc) => {
         let data;
         try {
@@ -1061,11 +1073,11 @@ export function getOpenGraphMetadata(url) {
     };
 }
 
-export function doPostAction(postId, actionId, selectedOption = '') {
+export function doPostAction(postId: string, actionId: string, selectedOption = '') {
     return doPostActionWithCookie(postId, actionId, '', selectedOption);
 }
 
-export function doPostActionWithCookie(postId, actionId, actionCookie, selectedOption = '') {
+export function doPostActionWithCookie(postId: string, actionId: string, actionCookie: string, selectedOption = '') {
     return async (dispatch: DispatchFunc, getState: GetStateFunc) => {
         let data;
         try {
@@ -1087,7 +1099,7 @@ export function doPostActionWithCookie(postId, actionId, actionCookie, selectedO
     };
 }
 
-export function addMessageIntoHistory(message) {
+export function addMessageIntoHistory(message: string) {
     return async (dispatch: DispatchFunc, getState: GetStateFunc) => {
         dispatch({
             type: PostTypes.ADD_MESSAGE_INTO_HISTORY,
@@ -1098,7 +1110,7 @@ export function addMessageIntoHistory(message) {
     };
 }
 
-export function resetHistoryIndex(index) {
+export function resetHistoryIndex(index: number) {
     return async (dispatch: DispatchFunc, getState: GetStateFunc) => {
         dispatch({
             type: PostTypes.RESET_HISTORY_INDEX,
@@ -1109,7 +1121,7 @@ export function resetHistoryIndex(index) {
     };
 }
 
-export function moveHistoryIndexBack(index) {
+export function moveHistoryIndexBack(index: number) {
     return async (dispatch: DispatchFunc, getState: GetStateFunc) => {
         dispatch({
             type: PostTypes.MOVE_HISTORY_INDEX_BACK,
@@ -1120,7 +1132,7 @@ export function moveHistoryIndexBack(index) {
     };
 }
 
-export function moveHistoryIndexForward(index) {
+export function moveHistoryIndexForward(index: number) {
     return async (dispatch: DispatchFunc, getState: GetStateFunc) => {
         dispatch({
             type: PostTypes.MOVE_HISTORY_INDEX_FORWARD,
@@ -1131,7 +1143,7 @@ export function moveHistoryIndexForward(index) {
     };
 }
 
-export function handleNewPost(msg) {
+export function handleNewPost(msg: Omit<GenericAction, 'type'>) {
     return async (dispatch: DispatchFunc, getState: GetStateFunc) => {
         const state = getState();
         const currentUserId = getCurrentUserId(state);
@@ -1156,7 +1168,7 @@ export function handleNewPost(msg) {
     };
 }
 
-function completePostReceive(post: Post, websocketMessageProps) {
+function completePostReceive(post: Post, websocketMessageProps: any) {
     return (dispatch: DispatchFunc, getState: GetStateFunc) => {
         const state = getState();
         const rootPost = Selectors.getPost(state, post.root_id);
@@ -1169,7 +1181,7 @@ function completePostReceive(post: Post, websocketMessageProps) {
     };
 }
 
-function lastPostActions(post, websocketMessageProps) {
+function lastPostActions(post: Post, websocketMessageProps: any) {
     return async (dispatch: DispatchFunc, getState: GetStateFunc) => {
         const state = getState();
         const actions = [
diff --git a/src/actions/search.ts b/src/actions/search.ts
index 805a099f5..be05366ac 100644
--- a/src/actions/search.ts
+++ b/src/actions/search.ts
@@ -12,6 +12,7 @@ import {getProfilesAndStatusesForPosts, receivedPosts} from './posts';
 import {ActionResult, batchActions, DispatchFunc, GetStateFunc, ActionFunc} from 'types/actions';
 import {RelationOneToOne} from 'types/utilities';
 import {Post} from 'types/posts';
+import {SearchParameter} from 'types/search';
 const WEBAPP_SEARCH_PER_PAGE = 20;
 export function getMissingChannelsFromPosts(posts: RelationOneToOne<Post, Post>): ActionFunc {
     return async (dispatch: DispatchFunc, getState: GetStateFunc) => {
@@ -36,7 +37,7 @@ export function getMissingChannelsFromPosts(posts: RelationOneToOne<Post, Post>)
     };
 }
 
-export function searchPostsWithParams(teamId, params): ActionFunc {
+export function searchPostsWithParams(teamId: string, params: SearchParameter): ActionFunc {
     return async (dispatch: DispatchFunc, getState: GetStateFunc) => {
         const isGettingMore = params.page > 0;
         dispatch({
@@ -85,7 +86,7 @@ export function searchPostsWithParams(teamId, params): ActionFunc {
     };
 }
 
-export function searchPosts(teamId, terms, isOrSearch, includeDeletedChannels) {
+export function searchPosts(teamId: string, terms: string, isOrSearch: boolean, includeDeletedChannels: boolean) {
     return searchPostsWithParams(teamId, {terms, is_or_search: isOrSearch, include_deleted_channels: includeDeletedChannels, page: 0, per_page: WEBAPP_SEARCH_PER_PAGE});
 }
 
@@ -147,7 +148,7 @@ export function getFlaggedPosts(): ActionFunc {
     };
 }
 
-export function getPinnedPosts(channelId): ActionFunc {
+export function getPinnedPosts(channelId: string): ActionFunc {
     return async (dispatch: DispatchFunc, getState: GetStateFunc) => {
         dispatch({type: SearchTypes.SEARCH_PINNED_POSTS_REQUEST});
 
@@ -186,7 +187,7 @@ export function getPinnedPosts(channelId): ActionFunc {
     };
 }
 
-export function clearPinnedPosts(channelId): ActionFunc {
+export function clearPinnedPosts(channelId: string): ActionFunc {
     return async (dispatch) => {
         dispatch({
             type: SearchTypes.REMOVE_SEARCH_PINNED_POSTS,
@@ -245,7 +246,7 @@ export function getRecentMentions(): ActionFunc {
     };
 }
 
-export function removeSearchTerms(teamId, terms): ActionFunc {
+export function removeSearchTerms(teamId: string, terms: string): ActionFunc {
     return async (dispatch) => {
         dispatch({
             type: SearchTypes.REMOVE_SEARCH_TERM,
diff --git a/src/actions/teams.ts b/src/actions/teams.ts
index be32df7e6..b03d4bee3 100644
--- a/src/actions/teams.ts
+++ b/src/actions/teams.ts
@@ -13,7 +13,7 @@ import {getCurrentUserId} from 'selectors/entities/users';
 
 import {GetStateFunc, DispatchFunc, ActionFunc, ActionResult, batchActions, Action} from 'types/actions';
 
-import {Team} from 'types/teams';
+import {Team, TeamMembership} from 'types/teams';
 
 import {selectChannel} from './channels';
 import {logError} from './errors';
@@ -22,7 +22,7 @@ import {getProfilesByIds, getStatusesByIds} from './users';
 import {loadRolesIfNeeded} from './roles';
 import {UserProfile} from 'types/users';
 
-async function getProfilesAndStatusesForMembers(userIds, dispatch, getState) {
+async function getProfilesAndStatusesForMembers(userIds: string[], dispatch: DispatchFunc, getState: GetStateFunc) {
     const {
         currentUserId,
         profiles,
@@ -423,7 +423,7 @@ export function addUsersToTeam(teamId: string, userIds: Array<string>): ActionFu
         }
 
         const profiles: Partial<UserProfile>[] = [];
-        members.forEach((m) => profiles.push({id: m.user_id}));
+        members.forEach((m: TeamMembership) => profiles.push({id: m.user_id}));
 
         dispatch(batchActions([
             {
@@ -495,7 +495,7 @@ export function removeUserFromTeam(teamId: string, userId: string): ActionFunc {
     };
 }
 
-export function updateTeamMemberRoles(teamId: string, userId: string, roles: string): ActionFunc {
+export function updateTeamMemberRoles(teamId: string, userId: string, roles: string[]): ActionFunc {
     return async (dispatch: DispatchFunc, getState: GetStateFunc) => {
         try {
             await Client4.updateTeamMemberRoles(teamId, userId, roles);
diff --git a/src/actions/users.ts b/src/actions/users.ts
index 1987ca654..63e5bd631 100644
--- a/src/actions/users.ts
+++ b/src/actions/users.ts
@@ -1,7 +1,7 @@
 // Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
 // See LICENSE.txt for license information.
 import {Action, ActionFunc, ActionResult, batchActions, DispatchFunc, GetStateFunc} from 'types/actions';
-import {UserProfile} from 'types/users';
+import {UserProfile, UserStatus} from 'types/users';
 import {TeamMembership} from 'types/teams';
 import {Client4} from 'client';
 import {General} from '../constants';
@@ -21,6 +21,7 @@ import {getCurrentUserId, getUsers} from 'selectors/entities/users';
 import {logError} from './errors';
 import {bindClientFunc, forceLogoutIfNecessary, debounce} from './helpers';
 import {getMyPreferences, makeDirectChannelVisibleIfNecessary, makeGroupMessageVisibleIfNecessary} from './preferences';
+import {Dictionary} from 'types/utilities';
 export function checkMfa(loginId: string): ActionFunc {
     return async (dispatch: DispatchFunc, getState: GetStateFunc) => {
         dispatch({type: UserTypes.CHECK_MFA_REQUEST, data: null}, getState);
@@ -314,7 +315,7 @@ export function getMissingProfilesByUsernames(usernames: Array<string>): ActionF
         const usernameProfiles = Object.values(profiles).reduce((acc, profile: any) => {
             acc[profile.username] = profile;
             return acc;
-        }, {});
+        }, {} as Dictionary<UserProfile>);
         const missingUsernames: string[] = [];
         usernames.forEach((username) => {
             if (!usernameProfiles[username]) {
@@ -709,7 +710,7 @@ export function getStatus(userId: string): ActionFunc {
     });
 }
 
-export function setStatus(status: string): ActionFunc {
+export function setStatus(status: UserStatus): ActionFunc {
     return async (dispatch: DispatchFunc, getState: GetStateFunc) => {
         try {
             await Client4.updateStatus(status);
@@ -961,7 +962,7 @@ export function searchProfiles(term: string, options: any = {}): ActionFunc {
     };
 }
 
-let statusIntervalId;
+let statusIntervalId: NodeJS.Timeout|null;
 export function startPeriodicStatusUpdates(): ActionFunc {
     return async (dispatch: DispatchFunc, getState: GetStateFunc) => {
         if (statusIntervalId) {
diff --git a/src/actions/websocket.ts b/src/actions/websocket.ts
index b25f77f9e..7b9f8d0b8 100644
--- a/src/actions/websocket.ts
+++ b/src/actions/websocket.ts
@@ -22,7 +22,10 @@ import {getTeam, getMyTeamUnreads, getMyTeams, getMyTeamMembers} from './teams';
 import {getPost, getPosts, getProfilesAndStatusesForPosts, getCustomEmojiForReaction, handleNewPost, postDeleted, receivedPost} from './posts';
 import {fetchMyChannelsAndMembers, getChannelAndMyMember, getChannelStats, markChannelAsRead} from './channels';
 import {checkForModifiedUsers, getMe, getProfilesByIds, getStatusesByIds, loadProfilesForDirect} from './users';
-let doDispatch;
+import {ChannelMembership} from 'types/channels';
+import {Dictionary} from 'types/utilities';
+import {PreferenceType} from 'types/preferences';
+let doDispatch: DispatchFunc;
 export function init(platform: PlatformType, siteUrl: string | undefined | null, token: string | undefined | null, optionalWebSocket: any, additionalOptions: any = {}) {
     return async (dispatch: DispatchFunc, getState: GetStateFunc) => {
         const config = getConfig(getState());
@@ -138,7 +141,7 @@ export function doReconnect(now: number) {
                 dispatch(loadProfilesForDirect());
 
                 if (data && data.members) {
-                    const stillMemberOfCurrentChannel = data.members.find((m) => m.channel_id === currentChannelId);
+                    const stillMemberOfCurrentChannel = data.members.find((m: ChannelMembership) => m.channel_id === currentChannelId);
 
                     if (!stillMemberOfCurrentChannel) {
                         EventEmitter.emit(General.SWITCH_TO_DEFAULT_CHANNEL, currentTeamId);
@@ -186,7 +189,7 @@ function handleReconnect() {
     doDispatch(doReconnect(Date.now()));
 }
 
-function handleClose(connectFailCount) {
+function handleClose(connectFailCount: number) {
     doDispatch({
         type: GeneralTypes.WEBSOCKET_FAILURE,
         error: connectFailCount,
@@ -195,7 +198,21 @@ function handleClose(connectFailCount) {
     });
 }
 
-function handleEvent(msg) {
+export type WebsocketBroadcast = {
+    omit_users: Dictionary<boolean>;
+    user_id: string;
+    channel_id: string;
+    team_id: string;
+}
+
+export type WebSocketMessage = {
+    event: string;
+    data: any;
+    broadcast: WebsocketBroadcast;
+    seq: number;
+}
+
+function handleEvent(msg: WebSocketMessage) {
     switch (msg.event) {
     case WebsocketEvents.POSTED:
     case WebsocketEvents.EPHEMERAL_MESSAGE:
@@ -297,7 +314,7 @@ function handleEvent(msg) {
     }
 }
 
-function handleNewPostEvent(msg) {
+function handleNewPostEvent(msg: WebSocketMessage) {
     return (dispatch: DispatchFunc, getState: GetStateFunc) => {
         const post = JSON.parse(msg.data.post);
 
@@ -314,7 +331,7 @@ function handleNewPostEvent(msg) {
     };
 }
 
-function handlePostEdited(msg) {
+function handlePostEdited(msg: WebSocketMessage) {
     return (dispatch: DispatchFunc, getState: GetStateFunc) => {
         const data = JSON.parse(msg.data.post);
 
@@ -324,13 +341,13 @@ function handlePostEdited(msg) {
     };
 }
 
-function handlePostDeleted(msg) {
+function handlePostDeleted(msg: WebSocketMessage) {
     const data = JSON.parse(msg.data.post);
 
     return postDeleted(data);
 }
 
-function handleLeaveTeamEvent(msg) {
+function handleLeaveTeamEvent(msg: Partial<WebSocketMessage>) {
     return (dispatch: DispatchFunc, getState: GetStateFunc) => {
         const state = getState();
         const teams = getTeamsSelector(state);
@@ -349,15 +366,15 @@ function handleLeaveTeamEvent(msg) {
     };
 }
 
-function handleUpdateTeamEvent(msg) {
+function handleUpdateTeamEvent(msg: WebSocketMessage) {
     return {
         type: TeamTypes.UPDATED_TEAM,
         data: JSON.parse(msg.data.team),
     };
 }
 
-function handleTeamAddedEvent(msg) {
-    return async (dispatch) => {
+function handleTeamAddedEvent(msg: WebSocketMessage) {
+    return async (dispatch: DispatchFunc) => {
         await Promise.all([
             dispatch(getTeam(msg.data.team_id)),
             dispatch(getMyTeamUnreads()),
@@ -366,7 +383,7 @@ function handleTeamAddedEvent(msg) {
     };
 }
 
-function handleUserAddedEvent(msg) {
+function handleUserAddedEvent(msg: WebSocketMessage) {
     return (dispatch: DispatchFunc, getState: GetStateFunc) => {
         const state = getState();
         const currentChannelId = getCurrentChannelId(state);
@@ -393,7 +410,7 @@ function handleUserAddedEvent(msg) {
     };
 }
 
-function handleUserRemovedEvent(msg) {
+function handleUserRemovedEvent(msg: WebSocketMessage) {
     return (dispatch: DispatchFunc, getState: GetStateFunc) => {
         const state = getState();
         const channels = getAllChannels(state);
@@ -437,7 +454,7 @@ function handleUserRemovedEvent(msg) {
     };
 }
 
-function handleUserUpdatedEvent(msg) {
+function handleUserUpdatedEvent(msg: WebSocketMessage) {
     return (dispatch: DispatchFunc, getState: GetStateFunc) => {
         const currentUser = getCurrentUser(getState());
         const user = msg.data.user;
@@ -460,7 +477,7 @@ function handleUserUpdatedEvent(msg) {
     };
 }
 
-function handleRoleAddedEvent(msg) {
+function handleRoleAddedEvent(msg: WebSocketMessage) {
     const role = JSON.parse(msg.data.role);
 
     return {
@@ -469,7 +486,7 @@ function handleRoleAddedEvent(msg) {
     };
 }
 
-function handleRoleRemovedEvent(msg) {
+function handleRoleRemovedEvent(msg: WebSocketMessage) {
     const role = JSON.parse(msg.data.role);
 
     return {
@@ -478,7 +495,7 @@ function handleRoleRemovedEvent(msg) {
     };
 }
 
-function handleRoleUpdatedEvent(msg) {
+function handleRoleUpdatedEvent(msg: WebSocketMessage) {
     const role = JSON.parse(msg.data.role);
 
     return {
@@ -487,7 +504,7 @@ function handleRoleUpdatedEvent(msg) {
     };
 }
 
-function handleChannelCreatedEvent(msg) {
+function handleChannelCreatedEvent(msg: WebSocketMessage) {
     return (dispatch: DispatchFunc, getState: GetStateFunc) => {
         const {channel_id: channelId, team_id: teamId} = msg.data;
         const state = getState();
@@ -501,7 +518,7 @@ function handleChannelCreatedEvent(msg) {
     };
 }
 
-function handleChannelDeletedEvent(msg) {
+function handleChannelDeletedEvent(msg: WebSocketMessage) {
     return (dispatch: DispatchFunc, getState: GetStateFunc) => {
         const state = getState();
         const currentChannelId = getCurrentChannelId(state);
@@ -527,7 +544,7 @@ function handleChannelDeletedEvent(msg) {
     };
 }
 
-function handleChannelUpdatedEvent(msg) {
+function handleChannelUpdatedEvent(msg: WebSocketMessage) {
     return async (dispatch: DispatchFunc, getState: GetStateFunc) => {
         let channel;
         try {
@@ -555,7 +572,7 @@ function handleChannelUpdatedEvent(msg) {
 
 // handleChannelConvertedEvent handles updating of channel which is converted from public to private
 
-function handleChannelConvertedEvent(msg) {
+function handleChannelConvertedEvent(msg: WebSocketMessage) {
     return (dispatch: DispatchFunc, getState: GetStateFunc) => {
         const channelId = msg.data.channel_id;
         if (channelId) {
@@ -571,7 +588,7 @@ function handleChannelConvertedEvent(msg) {
     };
 }
 
-function handleChannelViewedEvent(msg) {
+function handleChannelViewedEvent(msg: WebSocketMessage) {
     return (dispatch: DispatchFunc, getState: GetStateFunc) => {
         const state = getState();
         const {channel_id: channelId} = msg.data;
@@ -585,7 +602,7 @@ function handleChannelViewedEvent(msg) {
     };
 }
 
-function handleChannelMemberUpdatedEvent(msg) {
+function handleChannelMemberUpdatedEvent(msg: WebSocketMessage) {
     const channelMember = JSON.parse(msg.data.channelMember);
 
     return {
@@ -594,15 +611,15 @@ function handleChannelMemberUpdatedEvent(msg) {
     };
 }
 
-function handleDirectAddedEvent(msg) {
-    return (dispatch) => {
+function handleDirectAddedEvent(msg: WebSocketMessage) {
+    return (dispatch: DispatchFunc) => {
         dispatch(getChannelAndMyMember(msg.broadcast.channel_id));
         return {data: true};
     };
 }
 
-function handlePreferenceChangedEvent(msg) {
-    return (dispatch) => {
+function handlePreferenceChangedEvent(msg: WebSocketMessage) {
+    return (dispatch: DispatchFunc) => {
         const preference = JSON.parse(msg.data.preference);
         dispatch({type: PreferenceTypes.RECEIVED_PREFERENCES, data: [preference]});
 
@@ -611,9 +628,9 @@ function handlePreferenceChangedEvent(msg) {
     };
 }
 
-function handlePreferencesChangedEvent(msg) {
+function handlePreferencesChangedEvent(msg: WebSocketMessage) {
     return (dispatch: DispatchFunc, getState: GetStateFunc) => {
-        const preferences = JSON.parse(msg.data.preferences);
+        const preferences = JSON.parse(msg.data.preferences) as PreferenceType[];
         const posts = getAllPosts(getState());
 
         preferences.forEach((pref) => {
@@ -628,20 +645,20 @@ function handlePreferencesChangedEvent(msg) {
     };
 }
 
-function handlePreferencesDeletedEvent(msg) {
+function handlePreferencesDeletedEvent(msg: WebSocketMessage) {
     const preferences = JSON.parse(msg.data.preferences);
 
     return {type: PreferenceTypes.DELETED_PREFERENCES, data: preferences};
 }
 
-function handleStatusChangedEvent(msg) {
+function handleStatusChangedEvent(msg: WebSocketMessage) {
     return {
         type: UserTypes.RECEIVED_STATUSES,
         data: [{user_id: msg.data.user_id, status: msg.data.status}],
     };
 }
 
-function handleHelloEvent(msg) {
+function handleHelloEvent(msg: WebSocketMessage) {
     const serverVersion = msg.data.server_version;
     if (serverVersion && Client4.serverVersion !== serverVersion) {
         Client4.serverVersion = serverVersion;
@@ -649,7 +666,7 @@ function handleHelloEvent(msg) {
     }
 }
 
-function handleUserTypingEvent(msg) {
+function handleUserTypingEvent(msg: WebSocketMessage) {
     return (dispatch: DispatchFunc, getState: GetStateFunc) => {
         const state = getState();
         const profiles = getUsers(state);
@@ -674,7 +691,7 @@ function handleUserTypingEvent(msg) {
                 type: WebsocketEvents.STOP_TYPING,
                 data,
             });
-        }, parseInt(config.TimeBetweenUserTypingUpdatesMilliseconds, 10));
+        }, parseInt(config.TimeBetweenUserTypingUpdatesMilliseconds!, 10));
 
         if (!profiles[userId] && userId !== currentUserId) {
             dispatch(getProfilesByIds([userId]));
@@ -688,8 +705,8 @@ function handleUserTypingEvent(msg) {
     };
 }
 
-function handleReactionAddedEvent(msg) {
-    return (dispatch) => {
+function handleReactionAddedEvent(msg: WebSocketMessage) {
+    return (dispatch: DispatchFunc) => {
         const {data} = msg;
         const reaction = JSON.parse(data.reaction);
 
@@ -703,7 +720,7 @@ function handleReactionAddedEvent(msg) {
     };
 }
 
-function handleReactionRemovedEvent(msg) {
+function handleReactionRemovedEvent(msg: WebSocketMessage) {
     const {data} = msg;
     const reaction = JSON.parse(data.reaction);
 
@@ -713,7 +730,7 @@ function handleReactionRemovedEvent(msg) {
     };
 }
 
-function handleAddEmoji(msg) {
+function handleAddEmoji(msg: WebSocketMessage) {
     const data = JSON.parse(msg.data.emoji);
 
     return {
@@ -722,7 +739,7 @@ function handleAddEmoji(msg) {
     };
 }
 
-function handleLicenseChangedEvent(msg) {
+function handleLicenseChangedEvent(msg: WebSocketMessage) {
     const data = msg.data.license;
 
     return {
@@ -731,7 +748,7 @@ function handleLicenseChangedEvent(msg) {
     };
 }
 
-function handleConfigChangedEvent(msg) {
+function handleConfigChangedEvent(msg: WebSocketMessage) {
     const data = msg.data.config;
 
     EventEmitter.emit(General.CONFIG_CHANGED, data);
@@ -741,7 +758,7 @@ function handleConfigChangedEvent(msg) {
     };
 }
 
-function handlePluginStatusesChangedEvent(msg) {
+function handlePluginStatusesChangedEvent(msg: WebSocketMessage) {
     const data = msg.data;
 
     return {
@@ -750,8 +767,8 @@ function handlePluginStatusesChangedEvent(msg) {
     };
 }
 
-function handleOpenDialogEvent(msg) {
-    return (dispatch) => {
+function handleOpenDialogEvent(msg: WebSocketMessage) {
+    return (dispatch: DispatchFunc) => {
         const data = (msg.data && msg.data.dialog) || {};
         dispatch({type: IntegrationTypes.RECEIVED_DIALOG, data: JSON.parse(data)});
         return {data: true};
@@ -759,7 +776,7 @@ function handleOpenDialogEvent(msg) {
 }
 
 // Helpers
-function getAddedDmUsersIfNecessary(preferences) {
+function getAddedDmUsersIfNecessary(preferences: PreferenceType[]) {
     return (dispatch: DispatchFunc, getState: GetStateFunc) => {
         const userIds: string[] = [];
 
@@ -811,8 +828,8 @@ export function userTyping(channelId: string, parentPostId: string): ActionFunc
         const stats = getCurrentChannelStats(state);
         const membersInChannel = stats ? stats.member_count : 0;
 
-        if (((t - lastTimeTypingSent) > config.TimeBetweenUserTypingUpdatesMilliseconds) &&
-            (membersInChannel < config.MaxNotificationsPerChannel) && (config.EnableUserTypingMessages === 'true')) {
+        if (((t - lastTimeTypingSent) > parseInt(config.TimeBetweenUserTypingUpdatesMilliseconds!, 10)) &&
+            (membersInChannel < parseInt(config.MaxNotificationsPerChannel!, 10)) && (config.EnableUserTypingMessages === 'true')) {
             websocketClient.userTyping(channelId, parentPostId);
             lastTimeTypingSent = t;
         }
diff --git a/src/client/client4.ts b/src/client/client4.ts
index f56a18f15..7e5c05301 100644
--- a/src/client/client4.ts
+++ b/src/client/client4.ts
@@ -8,7 +8,7 @@ import {General} from '../constants';
 import {isSystemAdmin} from 'utils/user_utils';
 
 import fetch from './fetch_etag';
-import {UserProfile} from 'types/users';
+import {UserProfile, UserStatus} from 'types/users';
 import {Team} from 'types/teams';
 import {Channel} from 'types/channels';
 import {Post} from 'types/posts';
@@ -16,6 +16,13 @@ import {Job} from 'types/jobs';
 import {Role} from 'types/roles';
 import {Scheme} from 'types/schemes';
 import {Options} from 'types/client4';
+import {PreferenceType} from 'types/preferences';
+import {IncomingWebhook, OutgoingWebhook, Command, OAuthApp, DialogSubmission} from 'types/integrations';
+import {CustomEmoji} from 'types/emojis';
+import {Config} from 'types/config';
+import {Bot, BotPatch} from 'types/bots';
+import {Dictionary} from 'types/utilities';
+import {SyncablePatch} from 'types/groups';
 
 const FormData = require('form-data');
 const HEADER_AUTH = 'Authorization';
@@ -238,7 +245,7 @@ export default class Client4 {
         return `${this.getBaseRoute()}/brand`;
     }
 
-    getBrandImageUrl(timestamp) {
+    getBrandImageUrl(timestamp: string) {
         return `${this.getBrandRoute()}/image?t=${timestamp}`;
     }
 
@@ -789,7 +796,7 @@ export default class Client4 {
         );
     };
 
-    searchUsers = (term: string, options) => {
+    searchUsers = (term: string, options: any) => {
         this.trackEvent('api', 'api_search_users');
 
         return this.doFetch(
@@ -812,7 +819,7 @@ export default class Client4 {
         );
     };
 
-    updateStatus = async (status) => {
+    updateStatus = async (status: UserStatus) => {
         return this.doFetch(
             `${this.getUserRoute(status.user_id)}/status`,
             {method: 'put', body: JSON.stringify(status)}
@@ -1158,7 +1165,7 @@ export default class Client4 {
         );
     };
 
-    updateTeamMemberRoles = async (teamId: string, userId: string, roles) => {
+    updateTeamMemberRoles = async (teamId: string, userId: string, roles: string[]) => {
         this.trackEvent('api', 'api_teams_update_member_roles', {team_id: teamId});
 
         return this.doFetch(
@@ -1185,7 +1192,7 @@ export default class Client4 {
         );
     };
 
-    importTeam = async (teamId: string, file, importFrom) => {
+    importTeam = async (teamId: string, file: File, importFrom: string) => {
         const formData = new FormData();
         formData.append('file', file, file.name);
         formData.append('filesize', file.size);
@@ -1327,7 +1334,7 @@ export default class Client4 {
         );
     };
 
-    updateChannelPrivacy = async (channelId: string, privacy) => {
+    updateChannelPrivacy = async (channelId: string, privacy: any) => {
         this.trackEvent('api', 'api_channels_update_privacy', {channel_id: channelId, privacy});
 
         return this.doFetch(
@@ -1345,7 +1352,7 @@ export default class Client4 {
         );
     };
 
-    updateChannelNotifyProps = async (props) => {
+    updateChannelNotifyProps = async (props: any) => {
         this.trackEvent('api', 'api_users_update_channel_notifcations', {channel_id: props.channel_id});
 
         return this.doFetch(
@@ -1465,7 +1472,7 @@ export default class Client4 {
         );
     };
 
-    updateChannelMemberRoles = async (channelId: string, userId: string, roles) => {
+    updateChannelMemberRoles = async (channelId: string, userId: string, roles: string) => {
         return this.doFetch(
             `${this.getChannelMemberRoute(channelId, userId)}/roles`,
             {method: 'put', body: JSON.stringify({roles})}
@@ -1697,7 +1704,7 @@ export default class Client4 {
         );
     };
 
-    searchPostsWithParams = async (teamId: string, params) => {
+    searchPostsWithParams = async (teamId: string, params: any) => {
         this.trackEvent('api', 'api_posts_search', {team_id: teamId});
 
         return this.doFetch(
@@ -1721,7 +1728,7 @@ export default class Client4 {
         return this.doPostActionWithCookie(postId, actionId, '', selectedOption);
     };
 
-    doPostActionWithCookie = async (postId: string, actionId: string, actionCookie, selectedOption = '') => {
+    doPostActionWithCookie = async (postId: string, actionId: string, actionCookie: string, selectedOption = '') => {
         if (selectedOption) {
             this.trackEvent('api', 'api_interactive_messages_menu_selected');
         } else {
@@ -1769,7 +1776,7 @@ export default class Client4 {
         return url;
     }
 
-    uploadFile = async (fileFormData, formBoundary) => {
+    uploadFile = async (fileFormData: any, formBoundary: string) => {
         this.trackEvent('api', 'api_files_upload');
         const request: any = {
             method: 'post',
@@ -1797,7 +1804,7 @@ export default class Client4 {
 
     // Preference Routes
 
-    savePreferences = async (userId: string, preferences) => {
+    savePreferences = async (userId: string, preferences: PreferenceType[]) => {
         return this.doFetch(
             `${this.getPreferencesRoute(userId)}`,
             {method: 'put', body: JSON.stringify(preferences)}
@@ -1811,7 +1818,7 @@ export default class Client4 {
         );
     };
 
-    deletePreferences = async (userId: string, preferences) => {
+    deletePreferences = async (userId: string, preferences: PreferenceType[]) => {
         return this.doFetch(
             `${this.getPreferencesRoute(userId)}/delete`,
             {method: 'post', body: JSON.stringify(preferences)}
@@ -1877,7 +1884,7 @@ export default class Client4 {
 
     // Integration Routes
 
-    createIncomingWebhook = async (hook) => {
+    createIncomingWebhook = async (hook: IncomingWebhook) => {
         this.trackEvent('api', 'api_integrations_created', {team_id: hook.team_id});
 
         return this.doFetch(
@@ -1918,7 +1925,7 @@ export default class Client4 {
         );
     };
 
-    updateIncomingWebhook = async (hook) => {
+    updateIncomingWebhook = async (hook: IncomingWebhook) => {
         this.trackEvent('api', 'api_integrations_updated', {team_id: hook.team_id});
 
         return this.doFetch(
@@ -1927,7 +1934,7 @@ export default class Client4 {
         );
     };
 
-    createOutgoingWebhook = async (hook) => {
+    createOutgoingWebhook = async (hook: OutgoingWebhook) => {
         this.trackEvent('api', 'api_integrations_created', {team_id: hook.team_id});
 
         return this.doFetch(
@@ -1972,7 +1979,7 @@ export default class Client4 {
         );
     };
 
-    updateOutgoingWebhook = async (hook) => {
+    updateOutgoingWebhook = async (hook: OutgoingWebhook) => {
         this.trackEvent('api', 'api_integrations_updated', {team_id: hook.team_id});
 
         return this.doFetch(
@@ -2009,7 +2016,7 @@ export default class Client4 {
         );
     };
 
-    executeCommand = async (command, commandArgs = {}) => {
+    executeCommand = async (command: Command, commandArgs = {}) => {
         this.trackEvent('api', 'api_integrations_used');
 
         return this.doFetch(
@@ -2018,7 +2025,7 @@ export default class Client4 {
         );
     };
 
-    addCommand = async (command) => {
+    addCommand = async (command: Command) => {
         this.trackEvent('api', 'api_integrations_created');
 
         return this.doFetch(
@@ -2027,7 +2034,7 @@ export default class Client4 {
         );
     };
 
-    editCommand = async (command) => {
+    editCommand = async (command: Command) => {
         this.trackEvent('api', 'api_integrations_created');
 
         return this.doFetch(
@@ -2052,7 +2059,7 @@ export default class Client4 {
         );
     };
 
-    createOAuthApp = async (app) => {
+    createOAuthApp = async (app: OAuthApp) => {
         this.trackEvent('api', 'api_apps_register');
 
         return this.doFetch(
@@ -2061,7 +2068,7 @@ export default class Client4 {
         );
     };
 
-    editOAuthApp = async (app) => {
+    editOAuthApp = async (app: OAuthApp) => {
         return this.doFetch(
             `${this.getOAuthAppsRoute()}/${app.id}`,
             {method: 'put', body: JSON.stringify(app)}
@@ -2105,7 +2112,7 @@ export default class Client4 {
         );
     };
 
-    submitInteractiveDialog = async (data) => {
+    submitInteractiveDialog = async (data: DialogSubmission) => {
         this.trackEvent('api', 'api_interactive_messages_dialog_submitted');
         return this.doFetch(
             `${this.getBaseRoute()}/actions/dialogs/submit`,
@@ -2115,7 +2122,7 @@ export default class Client4 {
 
     // Emoji Routes
 
-    createCustomEmoji = async (emoji, imageData: File) => {
+    createCustomEmoji = async (emoji: CustomEmoji, imageData: File) => {
         this.trackEvent('api', 'api_emoji_custom_add');
 
         const formData = new FormData();
@@ -2268,7 +2275,7 @@ export default class Client4 {
         );
     };
 
-    updateConfig = async (config) => {
+    updateConfig = async (config: Config) => {
         return this.doFetch(
             `${this.getBaseRoute()}/config`,
             {method: 'put', body: JSON.stringify(config)}
@@ -2289,7 +2296,7 @@ export default class Client4 {
         );
     };
 
-    testEmail = async (config) => {
+    testEmail = async (config: Config) => {
         return this.doFetch(
             `${this.getBaseRoute()}/email/test`,
             {method: 'post', body: JSON.stringify(config)}
@@ -2303,7 +2310,7 @@ export default class Client4 {
         );
     };
 
-    testS3Connection = async (config) => {
+    testS3Connection = async (config: Config) => {
         return this.doFetch(
             `${this.getBaseRoute()}/file/s3_test`,
             {method: 'post', body: JSON.stringify(config)}
@@ -2482,7 +2489,7 @@ export default class Client4 {
         );
     };
 
-    testElasticsearch = async (config) => {
+    testElasticsearch = async (config: Config) => {
         return this.doFetch(
             `${this.getBaseRoute()}/elasticsearch/test`,
             {method: 'post', body: JSON.stringify(config)}
@@ -2666,7 +2673,7 @@ export default class Client4 {
         );
     };
 
-    getMarketplacePlugins = async (filter) => {
+    getMarketplacePlugins = async (filter: string) => {
         return this.doFetch(
             `${this.getPluginsMarketplaceRoute()}${buildQueryString({filter: filter || ''})}`,
             {method: 'get'}
@@ -2710,7 +2717,7 @@ export default class Client4 {
 
     // Groups
 
-    linkGroupSyncable = async (groupID: string, syncableID: string, syncableType: string, patch) => {
+    linkGroupSyncable = async (groupID: string, syncableID: string, syncableType: string, patch: SyncablePatch) => {
         return this.doFetch(
             `${this.getBaseRoute()}/groups/${groupID}/${syncableType}s/${syncableID}/link`,
             {method: 'post', body: JSON.stringify(patch)}
@@ -2793,7 +2800,7 @@ export default class Client4 {
 
     // Redirect Location
 
-    getRedirectLocation = async (urlParam) => {
+    getRedirectLocation = async (urlParam: string) => {
         if (!urlParam.length) {
             return Promise.resolve();
         }
@@ -2803,14 +2810,14 @@ export default class Client4 {
 
     // Bot Routes
 
-    createBot = async (bot) => {
+    createBot = async (bot: Bot) => {
         return this.doFetch(
             `${this.getBotsRoute()}`,
             {method: 'post', body: JSON.stringify(bot)}
         );
     }
 
-    patchBot = async (botUserId: string, botPatch) => {
+    patchBot = async (botUserId: string, botPatch: BotPatch) => {
         return this.doFetch(
             `${this.getBotRoute(botUserId)}`,
             {method: 'put', body: JSON.stringify(botPatch)}
@@ -2884,13 +2891,13 @@ export default class Client4 {
 
     // Client Helpers
 
-    doFetch = async (url: string, options) => {
+    doFetch = async (url: string, options: Options) => {
         const {data} = await this.doFetchWithResponse(url, options);
 
         return data;
     };
 
-    doFetchWithResponse = async (url: string, options) => {
+    doFetchWithResponse = async (url: string, options: Options) => {
         const response = await fetch(url, this.getOptions(options));
         const headers = parseAndMergeNestedHeaders(response.headers);
 
@@ -2944,7 +2951,7 @@ export default class Client4 {
         });
     };
 
-    trackEvent(category: string, event: string, props?) {
+    trackEvent(category: string, event: string, props?: any) {
         // Temporary change to allow only certain events to reduce data rate - see MM-13062
         if (![
             'api_posts_create',
@@ -2995,7 +3002,7 @@ export default class Client4 {
     }
 }
 
-function parseAndMergeNestedHeaders(originalHeaders) {
+function parseAndMergeNestedHeaders(originalHeaders: any) {
     const headers = new Map();
     let nestedHeaders = new Map();
     originalHeaders.forEach((val: string, key: string) => {
@@ -3019,7 +3026,7 @@ export class ClientError extends Error {
     intl: { defaultMessage: string; id: string } | { defaultMessage: string; id: string } | { id: string; defaultMessage: string; values: any } | { id: string; defaultMessage: string };
     server_error_id: any;
     status_code: any;
-    constructor(baseUrl: string, data) {
+    constructor(baseUrl: string, data: any) {
         super(data.message + ': ' + cleanUrlForLogging(baseUrl, data.url));
 
         this.message = data.message;
diff --git a/src/client/fetch_etag.ts b/src/client/fetch_etag.ts
index a4c178fd4..7d9f2bd1e 100644
--- a/src/client/fetch_etag.ts
+++ b/src/client/fetch_etag.ts
@@ -11,7 +11,7 @@ export default ((url?: string, options: Options = {headers: {}}) => {
         const etag = etags[url!];
         const cachedResponse = data[`${url}${etag}`]; // ensure etag is for url
         if (etag) {
-            options.headers['If-None-Match'] = etag;
+            options.headers!['If-None-Match'] = etag;
         }
 
         return fetch(url!, options).
diff --git a/src/client/websocket_client.ts b/src/client/websocket_client.ts
index 278cbfb89..a58f0f483 100644
--- a/src/client/websocket_client.ts
+++ b/src/client/websocket_client.ts
@@ -5,12 +5,12 @@ const MIN_WEBSOCKET_RETRY_TIME = 3000; // 3 sec
 
 const MAX_WEBSOCKET_RETRY_TIME = 300000; // 5 mins
 
-let Socket;
+let Socket: any;
 
 class WebSocketClient {
     conn?: WebSocket;
     connectionUrl: null;
-    token: null;
+    token: string|null;
     sequence: number;
     connectFailCount: number;
     eventCallback?: Function;
@@ -32,7 +32,7 @@ class WebSocketClient {
         this.platform = '';
     }
 
-    initialize(token, opts) {
+    initialize(token: string|null, opts: any) {
         const defaults = {
             forceConnection: true,
             connectionUrl: this.connectionUrl,
@@ -182,27 +182,27 @@ class WebSocketClient {
         });
     }
 
-    setConnectingCallback(callback) {
+    setConnectingCallback(callback: Function) {
         this.connectingCallback = callback;
     }
 
-    setEventCallback(callback) {
+    setEventCallback(callback: Function) {
         this.eventCallback = callback;
     }
 
-    setFirstConnectCallback(callback) {
+    setFirstConnectCallback(callback: Function) {
         this.firstConnectCallback = callback;
     }
 
-    setReconnectCallback(callback) {
+    setReconnectCallback(callback: Function) {
         this.reconnectCallback = callback;
     }
 
-    setErrorCallback(callback) {
+    setErrorCallback(callback: Function) {
         this.errorCallback = callback;
     }
 
-    setCloseCallback(callback) {
+    setCloseCallback(callback: Function) {
         this.closeCallback = callback;
     }
 
@@ -218,7 +218,7 @@ class WebSocketClient {
         }
     }
 
-    sendMessage(action, data) {
+    sendMessage(action: string, data: any) {
         const msg = {
             action,
             seq: this.sequence++,
@@ -233,7 +233,7 @@ class WebSocketClient {
         }
     }
 
-    userTyping(channelId, parentId) {
+    userTyping(channelId: string, parentId: string) {
         this.sendMessage('user_typing', {
             channel_id: channelId,
             parent_id: parentId,
@@ -244,7 +244,7 @@ class WebSocketClient {
         this.sendMessage('get_statuses', null);
     }
 
-    getStatusesByIds(userIds) {
+    getStatusesByIds(userIds: string[]) {
         this.sendMessage('get_statuses_by_ids', {
             user_ids: userIds,
         });
diff --git a/src/constants/files.ts b/src/constants/files.ts
index d5e860d9e..acc2a3dd5 100644
--- a/src/constants/files.ts
+++ b/src/constants/files.ts
@@ -1,6 +1,9 @@
 // Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
 // See LICENSE.txt for license information.
-export default {
+
+import {Dictionary} from 'types/utilities';
+
+const Files: Dictionary<string[]> = {
     AUDIO_TYPES: ['mp3', 'wav', 'wma', 'm4a', 'flac', 'aac', 'ogg'],
     CODE_TYPES: ['as', 'applescript', 'osascript', 'scpt', 'bash', 'sh', 'zsh', 'clj', 'boot', 'cl2', 'cljc', 'cljs', 'cljs.hl', 'cljscm', 'cljx', 'hic', 'coffee', '_coffee', 'cake', 'cjsx', 'cson', 'iced', 'cpp', 'c', 'cc', 'h', 'c++', 'h++', 'hpp', 'cs', 'csharp', 'css', 'd', 'di', 'dart', 'delphi', 'dpr', 'dfm', 'pas', 'pascal', 'freepascal', 'lazarus', 'lpr', 'lfm', 'diff', 'django', 'jinja', 'dockerfile', 'docker', 'erl', 'f90', 'f95', 'fsharp', 'fs', 'gcode', 'nc', 'go', 'groovy', 'handlebars', 'hbs', 'html.hbs', 'html.handlebars', 'hs', 'hx', 'java', 'jsp', 'js', 'jsx', 'json', 'jl', 'kt', 'ktm', 'kts', 'less', 'lisp', 'lua', 'mk', 'mak', 'md', 'mkdown', 'mkd', 'matlab', 'm', 'mm', 'objc', 'obj-c', 'ml', 'perl', 'pl', 'php', 'php3', 'php4', 'php5', 'php6', 'ps', 'ps1', 'pp', 'py', 'gyp', 'r', 'ruby', 'rb', 'gemspec', 'podspec', 'thor', 'irb', 'rs', 'scala', 'scm', 'sld', 'scss', 'st', 'sql', 'swift', 'tex', 'txt', 'vbnet', 'vb', 'bas', 'vbs', 'v', 'veo', 'xml', 'html', 'xhtml', 'rss', 'atom', 'xsl', 'plist', 'yaml'],
     IMAGE_TYPES: ['jpg', 'gif', 'bmp', 'png', 'jpeg', 'tiff', 'tif'],
@@ -11,3 +14,5 @@ export default {
     VIDEO_TYPES: ['mp4', 'avi', 'webm', 'mkv', 'wmv', 'mpg', 'mov', 'flv'],
     WORD_TYPES: ['doc', 'docx'],
 };
+
+export default Files;
\ No newline at end of file
diff --git a/src/constants/preferences.ts b/src/constants/preferences.ts
index 90fcd08fc..63ae5fa16 100644
--- a/src/constants/preferences.ts
+++ b/src/constants/preferences.ts
@@ -1,6 +1,9 @@
 // Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
 // See LICENSE.txt for license information.
-export default {
+
+import {Dictionary} from 'types/utilities';
+
+const Preferences: Dictionary<any> = {
     CATEGORY_CHANNEL_OPEN_TIME: 'channel_open_time',
     CATEGORY_CHANNEL_APPROXIMATE_VIEW_TIME: 'channel_approximate_view_time',
     CATEGORY_DIRECT_CHANNEL_SHOW: 'direct_channel_show',
@@ -145,3 +148,5 @@ export default {
         },
     },
 };
+
+export default Preferences;
\ No newline at end of file
diff --git a/src/reducers/entities/admin.ts b/src/reducers/entities/admin.ts
index 14f9955cd..42cc49233 100644
--- a/src/reducers/entities/admin.ts
+++ b/src/reducers/entities/admin.ts
@@ -5,8 +5,9 @@ import {combineReducers} from 'redux';
 import {AdminTypes, UserTypes} from 'action_types';
 import {Stats, Plugins} from '../../constants';
 import PluginState from '../../constants/plugins';
+import {GenericAction} from 'types/actions';
 
-function logs(state = [], action) {
+function logs(state = [], action: GenericAction) {
     switch (action.type) {
     case AdminTypes.RECEIVED_LOGS: {
         return action.data;
@@ -19,7 +20,7 @@ function logs(state = [], action) {
     }
 }
 
-function audits(state = {}, action) {
+function audits(state: any = {}, action: GenericAction) {
     switch (action.type) {
     case AdminTypes.RECEIVED_AUDITS: {
         const nextState = {...state};
@@ -36,7 +37,7 @@ function audits(state = {}, action) {
     }
 }
 
-function config(state: any = {}, action) {
+function config(state: any = {}, action: GenericAction) {
     switch (action.type) {
     case AdminTypes.RECEIVED_CONFIG: {
         return action.data;
@@ -63,7 +64,7 @@ function config(state: any = {}, action) {
     }
 }
 
-function environmentConfig(state = {}, action) {
+function environmentConfig(state: any = {}, action: GenericAction) {
     switch (action.type) {
     case AdminTypes.RECEIVED_ENVIRONMENT_CONFIG: {
         return action.data;
@@ -76,7 +77,7 @@ function environmentConfig(state = {}, action) {
     }
 }
 
-function complianceReports(state = {}, action) {
+function complianceReports(state: any = {}, action: GenericAction) {
     switch (action.type) {
     case AdminTypes.RECEIVED_COMPLIANCE_REPORT: {
         const nextState = {...state};
@@ -98,7 +99,7 @@ function complianceReports(state = {}, action) {
     }
 }
 
-function clusterInfo(state = [], action) {
+function clusterInfo(state = [], action: GenericAction) {
     switch (action.type) {
     case AdminTypes.RECEIVED_CLUSTER_STATUS: {
         return action.data;
@@ -111,7 +112,7 @@ function clusterInfo(state = [], action) {
     }
 }
 
-function samlCertStatus(state = {}, action) {
+function samlCertStatus(state: any = {}, action: GenericAction) {
     switch (action.type) {
     case AdminTypes.RECEIVED_SAML_CERT_STATUS: {
         return action.data;
@@ -124,8 +125,8 @@ function samlCertStatus(state = {}, action) {
     }
 }
 
-export function convertAnalyticsRowsToStats(data, name) {
-    const stats = {};
+export function convertAnalyticsRowsToStats(data: any, name: string) {
+    const stats: any = {};
     const clonedData = [...data];
 
     if (name === 'post_counts_day') {
@@ -210,7 +211,7 @@ export function convertAnalyticsRowsToStats(data, name) {
     return stats;
 }
 
-function analytics(state = {}, action) {
+function analytics(state: any = {}, action: GenericAction) {
     switch (action.type) {
     case AdminTypes.RECEIVED_SYSTEM_ANALYTICS: {
         const stats = convertAnalyticsRowsToStats(action.data, action.name);
@@ -224,7 +225,7 @@ function analytics(state = {}, action) {
     }
 }
 
-function teamAnalytics(state = {}, action) {
+function teamAnalytics(state: any = {}, action: GenericAction) {
     switch (action.type) {
     case AdminTypes.RECEIVED_TEAM_ANALYTICS: {
         const nextState = {...state};
@@ -241,13 +242,13 @@ function teamAnalytics(state = {}, action) {
     }
 }
 
-function userAccessTokens(state = {}, action) {
+function userAccessTokens(state: any = {}, action: GenericAction) {
     switch (action.type) {
     case AdminTypes.RECEIVED_USER_ACCESS_TOKEN: {
         return {...state, [action.data.id]: action.data};
     }
     case AdminTypes.RECEIVED_USER_ACCESS_TOKENS_FOR_USER: {
-        const nextState = {};
+        const nextState: any = {};
 
         for (const uat of action.data) {
             nextState[uat.id] = uat;
@@ -256,7 +257,7 @@ function userAccessTokens(state = {}, action) {
         return {...state, ...nextState};
     }
     case AdminTypes.RECEIVED_USER_ACCESS_TOKENS: {
-        const nextState = {};
+        const nextState: any = {};
 
         for (const uat of action.data) {
             nextState[uat.id] = uat;
@@ -284,7 +285,7 @@ function userAccessTokens(state = {}, action) {
     }
 }
 
-function userAccessTokensForUser(state = {}, action) {
+function userAccessTokensForUser(state: any = {}, action: GenericAction) {
     switch (action.type) {
     case AdminTypes.RECEIVED_USER_ACCESS_TOKEN: {
         const nextUserState = {...(state[action.data.user_id] || {})};
@@ -302,7 +303,7 @@ function userAccessTokensForUser(state = {}, action) {
         return {...state, [action.userId]: nextUserState};
     }
     case AdminTypes.RECEIVED_USER_ACCESS_TOKENS: {
-        const nextUserState = {};
+        const nextUserState: any = {};
 
         for (const uat of action.data) {
             nextUserState[uat.user_id] = nextUserState[uat.user_id] || {};
@@ -360,7 +361,7 @@ function userAccessTokensForUser(state = {}, action) {
     }
 }
 
-function plugins(state = {}, action) {
+function plugins(state: any = {}, action: GenericAction) {
     switch (action.type) {
     case AdminTypes.RECEIVED_PLUGINS: {
         const nextState = {...state};
@@ -406,10 +407,10 @@ function plugins(state = {}, action) {
     }
 }
 
-function pluginStatuses(state = {}, action) {
+function pluginStatuses(state: any = {}, action: GenericAction) {
     switch (action.type) {
     case AdminTypes.RECEIVED_PLUGIN_STATUSES: {
-        const nextState = {};
+        const nextState: any = {};
 
         for (const plugin of (action.data || [])) {
             const id = plugin.plugin_id;
@@ -492,7 +493,7 @@ function pluginStatuses(state = {}, action) {
     }
 }
 
-function ldapGroupsCount(state = {}, action) {
+function ldapGroupsCount(state: any = {}, action: GenericAction) {
     switch (action.type) {
     case AdminTypes.RECEIVED_LDAP_GROUPS:
         return action.data.count;
@@ -503,10 +504,10 @@ function ldapGroupsCount(state = {}, action) {
     }
 }
 
-function ldapGroups(state = {}, action) {
+function ldapGroups(state: any = {}, action: GenericAction) {
     switch (action.type) {
     case AdminTypes.RECEIVED_LDAP_GROUPS: {
-        const nextState = {};
+        const nextState: any = {};
         for (const group of action.data.groups) {
             nextState[group.primary_key] = group;
         }
diff --git a/src/reducers/entities/bots.ts b/src/reducers/entities/bots.ts
index 9f96f4312..837fb9586 100644
--- a/src/reducers/entities/bots.ts
+++ b/src/reducers/entities/bots.ts
@@ -2,8 +2,11 @@
 // See LICENSE.txt for license information.
 import {combineReducers} from 'redux';
 import {BotTypes, UserTypes} from 'action_types';
+import {GenericAction} from 'types/actions';
+import {Dictionary} from 'types/utilities';
+import {Bot} from 'types/bots';
 
-function accounts(state = {}, action) {
+function accounts(state: Dictionary<Bot> = {}, action: GenericAction) {
     switch (action.type) {
     case BotTypes.RECEIVED_BOT_ACCOUNTS: {
         const newBots = action.data;
diff --git a/src/reducers/entities/channels.ts b/src/reducers/entities/channels.ts
index 5f2c668b6..7556d4906 100644
--- a/src/reducers/entities/channels.ts
+++ b/src/reducers/entities/channels.ts
@@ -3,10 +3,14 @@
 import {combineReducers} from 'redux';
 import {ChannelTypes, UserTypes, SchemeTypes, GroupTypes} from 'action_types';
 import {General} from '../../constants';
+import {GenericAction} from 'types/actions';
+import {Channel, ChannelMembership, ChannelStats} from 'types/channels';
+import {RelationOneToMany, RelationOneToOne, IDMappedObjects, UserIDMappedObjects} from 'types/utilities';
+import {Team} from 'types/teams';
 
-function channelListToSet(state, action) {
+function channelListToSet(state: any, action: GenericAction) {
     const nextState = {...state};
-    action.data.forEach((channel) => {
+    action.data.forEach((channel: Channel) => {
         const nextSet = new Set(nextState[channel.team_id]);
         nextSet.add(channel.id);
         nextState[channel.team_id] = nextSet;
@@ -15,7 +19,7 @@ function channelListToSet(state, action) {
     return nextState;
 }
 
-function removeChannelFromSet(state, action) {
+function removeChannelFromSet(state: any, action: GenericAction) {
     const id = action.data.team_id;
     const nextSet = new Set(state[id]);
     nextSet.delete(action.data.id);
@@ -25,7 +29,7 @@ function removeChannelFromSet(state, action) {
     };
 }
 
-function currentChannelId(state = '', action) {
+function currentChannelId(state = '', action: GenericAction) {
     switch (action.type) {
     case ChannelTypes.SELECT_CHANNEL:
         return action.data;
@@ -36,7 +40,7 @@ function currentChannelId(state = '', action) {
     }
 }
 
-function channels(state = {}, action) {
+function channels(state: IDMappedObjects<Channel> = {}, action: GenericAction) {
     switch (action.type) {
     case ChannelTypes.RECEIVED_CHANNEL:
         if (state[action.data.id] && action.data.type === General.DM_CHANNEL) {
@@ -145,7 +149,7 @@ function channels(state = {}, action) {
     }
 }
 
-function channelsInTeam(state = {}, action) {
+function channelsInTeam(state: RelationOneToMany<Team, Channel> = {}, action: GenericAction) {
     switch (action.type) {
     case ChannelTypes.RECEIVED_CHANNEL: {
         const nextSet = new Set(state[action.data.team_id]);
@@ -171,7 +175,7 @@ function channelsInTeam(state = {}, action) {
     }
 }
 
-function myMembers(state = {}, action) {
+function myMembers(state: RelationOneToOne<Channel, ChannelMembership> = {}, action: GenericAction) {
     switch (action.type) {
     case ChannelTypes.RECEIVED_MY_CHANNEL_MEMBER: {
         const channelMember = action.data;
@@ -181,10 +185,10 @@ function myMembers(state = {}, action) {
         };
     }
     case ChannelTypes.RECEIVED_MY_CHANNEL_MEMBERS: {
-        const nextState = {...state};
-        const remove = action.remove;
+        const nextState: any = {...state};
+        const remove = action.remove as string[];
         if (remove) {
-            remove.forEach((id) => {
+            remove.forEach((id: string) => {
                 Reflect.deleteProperty(nextState, id);
             });
         }
@@ -310,7 +314,7 @@ function myMembers(state = {}, action) {
     }
 }
 
-function membersInChannel(state = {}, action) {
+function membersInChannel(state: RelationOneToOne<Channel, UserIDMappedObjects<ChannelMembership>> = {}, action: GenericAction) {
     switch (action.type) {
     case ChannelTypes.RECEIVED_MY_CHANNEL_MEMBER:
     case ChannelTypes.RECEIVED_CHANNEL_MEMBER: {
@@ -325,7 +329,7 @@ function membersInChannel(state = {}, action) {
     case ChannelTypes.RECEIVED_MY_CHANNEL_MEMBERS:
     case ChannelTypes.RECEIVED_CHANNEL_MEMBERS: {
         const nextState = {...state};
-        const remove = action.remove;
+        const remove = action.remove as string[];
         const currentUserId = action.currentUserId;
         if (remove && currentUserId) {
             remove.forEach((id) => {
@@ -372,7 +376,7 @@ function membersInChannel(state = {}, action) {
     }
 }
 
-function stats(state = {}, action) {
+function stats(state: RelationOneToOne<Channel, ChannelStats> = {}, action: GenericAction) {
     switch (action.type) {
     case ChannelTypes.RECEIVED_CHANNEL_STATS: {
         const nextState = {...state};
@@ -422,7 +426,7 @@ function stats(state = {}, action) {
     }
 }
 
-function groupsAssociatedToChannel(state = {}, action) {
+function groupsAssociatedToChannel(state: any = {}, action: GenericAction) {
     switch (action.type) {
     case GroupTypes.RECEIVED_GROUPS_ASSOCIATED_TO_CHANNEL: {
         const {channelID, groups, totalGroupCount} = action.data;
@@ -460,7 +464,7 @@ function groupsAssociatedToChannel(state = {}, action) {
     }
 }
 
-function updateChannelMemberSchemeRoles(state, action) {
+function updateChannelMemberSchemeRoles(state: any, action: GenericAction) {
     const {channelId, userId, isSchemeUser, isSchemeAdmin} = action.data;
     const channel = state[channelId];
     if (channel) {
@@ -482,7 +486,7 @@ function updateChannelMemberSchemeRoles(state, action) {
     return state;
 }
 
-function totalCount(state = 0, action) {
+function totalCount(state = 0, action: GenericAction) {
     switch (action.type) {
     case ChannelTypes.RECEIVED_TOTAL_CHANNEL_COUNT: {
         return action.data;
diff --git a/src/reducers/entities/files.ts b/src/reducers/entities/files.ts
index cdda1bc37..bda824d22 100644
--- a/src/reducers/entities/files.ts
+++ b/src/reducers/entities/files.ts
@@ -3,16 +3,20 @@
 
 import {combineReducers} from 'redux';
 import {FileTypes, PostTypes, UserTypes} from 'action_types';
+import {GenericAction} from 'types/actions';
+import {Post} from 'types/posts';
+import {FileInfo} from 'types/files';
+import {Dictionary} from 'types/utilities';
 
-export function files(state = {}, action) {
+export function files(state: Dictionary<FileInfo> = {}, action: GenericAction) {
     switch (action.type) {
     case FileTypes.RECEIVED_UPLOAD_FILES:
     case FileTypes.RECEIVED_FILES_FOR_POST: {
-        const filesById = action.data.reduce((filesMap, file) => {
+        const filesById = action.data.reduce((filesMap: any, file: any) => {
             return {...filesMap,
                 [file.id]: file,
             };
-        }, {});
+        }, {} as any);
         return {...state,
             ...filesById,
         };
@@ -35,7 +39,7 @@ export function files(state = {}, action) {
     case PostTypes.POST_REMOVED: {
         if (action.data && action.data.file_ids && action.data.file_ids.length) {
             const nextState = {...state};
-            const fileIds = action.data.file_ids;
+            const fileIds = action.data.file_ids as string[];
             fileIds.forEach((id) => {
                 Reflect.deleteProperty(nextState, id);
             });
@@ -53,7 +57,7 @@ export function files(state = {}, action) {
     }
 }
 
-function storeFilesForPost(state, post) {
+function storeFilesForPost(state: Dictionary<FileInfo>, post: Post) {
     if (!post.metadata || !post.metadata.files) {
         return state;
     }
@@ -71,13 +75,13 @@ function storeFilesForPost(state, post) {
     }, state);
 }
 
-export function fileIdsByPostId(state = {}, action) {
+export function fileIdsByPostId(state: Dictionary<Array<string>> = {}, action: GenericAction) {
     switch (action.type) {
     case FileTypes.RECEIVED_FILES_FOR_POST: {
         const {data, postId} = action;
-        const filesIdsForPost = data.map((file) => file.id);
+        const filesIdsForPost = data.map((file: FileInfo) => file.id);
         return {...state,
-            [postId]: filesIdsForPost,
+            [postId as string]: filesIdsForPost,
         };
     }
 
@@ -112,7 +116,7 @@ export function fileIdsByPostId(state = {}, action) {
     }
 }
 
-function storeFilesIdsForPost(state, post) {
+function storeFilesIdsForPost(state: Dictionary<string[]>, post: Post) {
     if (!post.metadata || !post.metadata.files) {
         return state;
     }
@@ -123,7 +127,7 @@ function storeFilesIdsForPost(state, post) {
     };
 }
 
-function filePublicLink(state = {}, action) {
+function filePublicLink(state: string | null = null, action: GenericAction) {
     switch (action.type) {
     case FileTypes.RECEIVED_FILE_PUBLIC_LINK: {
         return action.data;
diff --git a/src/reducers/entities/general.ts b/src/reducers/entities/general.ts
index dbe026a77..1aacc73f1 100644
--- a/src/reducers/entities/general.ts
+++ b/src/reducers/entities/general.ts
@@ -3,8 +3,10 @@
 
 import {combineReducers} from 'redux';
 import {GeneralTypes, UserTypes} from 'action_types';
+import {GenericAction} from 'types/actions';
+import {Config} from 'types/config';
 
-function config(state = {}, action) {
+function config(state: Partial<Config> = {}, action: GenericAction) {
     switch (action.type) {
     case GeneralTypes.CLIENT_CONFIG_RECEIVED:
         return Object.assign({}, state, action.data);
@@ -16,7 +18,7 @@ function config(state = {}, action) {
     }
 }
 
-function appState(state = false, action) {
+function appState(state = false, action: GenericAction) {
     switch (action.type) {
     case GeneralTypes.RECEIVED_APP_STATE:
         return action.data;
@@ -26,7 +28,7 @@ function appState(state = false, action) {
     }
 }
 
-function credentials(state = {}, action) {
+function credentials(state: any = {}, action: GenericAction) {
     switch (action.type) {
     case GeneralTypes.RECEIVED_APP_CREDENTIALS:
         return Object.assign({}, state, action.data);
@@ -38,7 +40,7 @@ function credentials(state = {}, action) {
     }
 }
 
-function dataRetentionPolicy(state = {}, action) {
+function dataRetentionPolicy(state: any = {}, action: GenericAction) {
     switch (action.type) {
     case GeneralTypes.RECEIVED_DATA_RETENTION_POLICY:
         return action.data;
@@ -49,7 +51,7 @@ function dataRetentionPolicy(state = {}, action) {
     }
 }
 
-function deviceToken(state = '', action) {
+function deviceToken(state = '', action: GenericAction) {
     switch (action.type) {
     case GeneralTypes.RECEIVED_APP_DEVICE_TOKEN:
         return action.data;
@@ -58,7 +60,7 @@ function deviceToken(state = '', action) {
     }
 }
 
-function license(state = {}, action) {
+function license(state: any = {}, action: GenericAction) {
     switch (action.type) {
     case GeneralTypes.CLIENT_LICENSE_RECEIVED:
         return action.data;
@@ -70,7 +72,7 @@ function license(state = {}, action) {
     }
 }
 
-function timezones(state = [], action) {
+function timezones(state: string[] = [], action: GenericAction) {
     switch (action.type) {
     case GeneralTypes.SUPPORTED_TIMEZONES_RECEIVED:
         return action.data;
@@ -81,7 +83,7 @@ function timezones(state = [], action) {
     }
 }
 
-function serverVersion(state = '', action) {
+function serverVersion(state = '', action: GenericAction) {
     switch (action.type) {
     case GeneralTypes.RECEIVED_SERVER_VERSION:
         return action.data;
diff --git a/src/reducers/entities/gifs.ts b/src/reducers/entities/gifs.ts
index b4f3ea69a..67e34f67b 100644
--- a/src/reducers/entities/gifs.ts
+++ b/src/reducers/entities/gifs.ts
@@ -3,78 +3,80 @@
 
 import {combineReducers} from 'redux';
 import {GifTypes} from 'action_types';
+import {GenericAction} from 'types/actions';
+import {Dictionary} from 'types/utilities';
 
-const SEARCH_SELECTORS = {
-    [GifTypes.SELECT_SEARCH_TEXT]: (state, action) => ({
+const SEARCH_SELECTORS: Dictionary<Function> = {
+    [GifTypes.SELECT_SEARCH_TEXT]: (state: any, action: GenericAction) => ({
         ...state,
         searchText: action.searchText,
     }),
-    [GifTypes.INVALIDATE_SEARCH_TEXT]: (state, action) => ({
+    [GifTypes.INVALIDATE_SEARCH_TEXT]: (state: any, action: GenericAction) => ({
         ...state,
         resultsByTerm: {
             ...state.resultsByTerm[action.searchText],
             didInvalidate: true,
         },
     }),
-    [GifTypes.REQUEST_SEARCH]: (state, action) => ({
+    [GifTypes.REQUEST_SEARCH]: (state: any, action: GenericAction) => ({
         ...state,
         resultsByTerm: TERM_SELECTOR[action.type](state.resultsByTerm, action),
     }),
-    [GifTypes.RECEIVE_SEARCH]: (state, action) => ({
+    [GifTypes.RECEIVE_SEARCH]: (state: any, action: GenericAction) => ({
         ...state,
         searchText: action.searchText,
         resultsByTerm: TERM_SELECTOR[action.type](state.resultsByTerm, action),
     }),
-    [GifTypes.RECEIVE_SEARCH_END]: (state, action) => ({
+    [GifTypes.RECEIVE_SEARCH_END]: (state: any, action: GenericAction) => ({
         ...state,
         searchText: action.searchText,
         resultsByTerm: TERM_SELECTOR[action.type](state.resultsByTerm, action),
     }),
-    [GifTypes.RECEIVE_CATEGORY_SEARCH]: (state, action) => ({
+    [GifTypes.RECEIVE_CATEGORY_SEARCH]: (state: any, action: GenericAction) => ({
         ...state,
         searchText: action.searchText,
         resultsByTerm: TERM_SELECTOR[action.type](state.resultsByTerm, action),
     }),
-    [GifTypes.SEARCH_FAILURE]: (state, action) => ({
+    [GifTypes.SEARCH_FAILURE]: (state: any, action: GenericAction) => ({
         ...state,
         searchText: action.searchText,
         resultsByTerm: TERM_SELECTOR[action.type](state.resultsByTerm, action),
     }),
-    [GifTypes.CLEAR_SEARCH_RESULTS]: (state) => ({
+    [GifTypes.CLEAR_SEARCH_RESULTS]: (state: any) => ({
         ...state,
         searchText: '',
         resultsByTerm: {},
     }),
-    [GifTypes.SAVE_SEARCH_SCROLL_POSITION]: (state, action) => ({
+    [GifTypes.SAVE_SEARCH_SCROLL_POSITION]: (state: any, action: GenericAction) => ({
         ...state,
         scrollPosition: action.scrollPosition,
     }),
-    [GifTypes.SAVE_SEARCH_PRIOR_LOCATION]: (state, action) => ({
+    [GifTypes.SAVE_SEARCH_PRIOR_LOCATION]: (state: any, action: GenericAction) => ({
         ...state,
         priorLocation: action.priorLocation,
     }),
-    [GifTypes.UPDATE_SEARCH_TEXT]: (state, action) => ({
+    [GifTypes.UPDATE_SEARCH_TEXT]: (state: any, action: GenericAction) => ({
         ...state,
         searchText: action.searchText,
     }),
-    [GifTypes.SAVE_SEARCH_BAR_TEXT]: (state, action) => ({
+    [GifTypes.SAVE_SEARCH_BAR_TEXT]: (state: any, action: GenericAction) => ({
         ...state,
         searchBarText: action.searchBarText,
     }),
 };
 
-const CATEGORIES_SELECTORS = {
-    [GifTypes.REQUEST_CATEGORIES_LIST]: (state) => ({
+const CATEGORIES_SELECTORS: Dictionary<Function> = {
+    [GifTypes.REQUEST_CATEGORIES_LIST]: (state: any) => ({
         ...state,
         isFetching: true,
     }),
-    [GifTypes.CATEGORIES_LIST_RECEIVED]: (state, action) => {
+    [GifTypes.CATEGORIES_LIST_RECEIVED]: (state: any, action: GenericAction) => {
         const {cursor, tags} = action;
         const {tagsList: oldTagsList = []} = state;
-        const tagsDict = {};
-        const newTagsList = tags.filter((item) => {
+        const tagsDict: any = {};
+        const newTagsList = tags.filter((item: any) => {
             return Boolean(item && item.gfycats[0] && item.gfycats[0].width);
-        }).map((item) => {
+        }).map((item: any) => {
             tagsDict[item.tag] = true;
             return {
                 tagName: item.tag,
@@ -91,14 +93,14 @@ const CATEGORIES_SELECTORS = {
             tagsDict,
         };
     },
-    [GifTypes.CATEGORIES_LIST_FAILURE]: (state) => ({
+    [GifTypes.CATEGORIES_LIST_FAILURE]: (state: any) => ({
         ...state,
         isFetching: false,
     }),
 };
 
-const TERM_SELECTOR = {
-    [GifTypes.REQUEST_SEARCH]: (state, action) => ({
+const TERM_SELECTOR: Dictionary<Function> = {
+    [GifTypes.REQUEST_SEARCH]: (state: any, action: GenericAction) => ({
         ...state,
         [action.searchText]: {
             ...state[action.searchText],
@@ -107,11 +109,11 @@ const TERM_SELECTOR = {
             pages: PAGE_SELECTOR[action.type](state[action.searchText], action),
         },
     }),
-    [GifTypes.RECEIVE_SEARCH]: (state, action) => {
-        const gfycats = action.gfycats.filter((item) => {
+    [GifTypes.RECEIVE_SEARCH]: (state: any, action: GenericAction) => {
+        const gfycats = action.gfycats.filter((item: any) => {
             return Boolean(item.gfyId && item.width && item.height);
         });
-        const newItems = gfycats.map((gfycat) => gfycat.gfyId);
+        const newItems = gfycats.map((gfycat: any) => gfycat.gfyId);
         return {
             ...state,
             [action.searchText]: {
@@ -138,11 +140,11 @@ const TERM_SELECTOR = {
             },
         };
     },
-    [GifTypes.RECEIVE_CATEGORY_SEARCH]: (state, action) => {
-        const gfycats = action.gfycats.filter((item) => {
+    [GifTypes.RECEIVE_CATEGORY_SEARCH]: (state: any, action: GenericAction) => {
+        const gfycats = action.gfycats.filter((item: any) => {
             return Boolean(item.gfyId && item.width && item.height);
         });
-        const newItems = gfycats.map((gfycat) => gfycat.gfyId);
+        const newItems = gfycats.map((gfycat: any) => gfycat.gfyId);
         return {
             ...state,
             [action.searchText]: {
@@ -157,7 +159,7 @@ const TERM_SELECTOR = {
             },
         };
     },
-    [GifTypes.RECEIVE_SEARCH_END]: (state, action) => ({
+    [GifTypes.RECEIVE_SEARCH_END]: (state: any, action: GenericAction) => ({
         ...state,
         [action.searchText]: {
             ...state[action.searchText],
@@ -165,7 +167,7 @@ const TERM_SELECTOR = {
             moreRemaining: false,
         },
     }),
-    [GifTypes.SEARCH_FAILURE]: (state, action) => ({
+    [GifTypes.SEARCH_FAILURE]: (state: any, action: GenericAction) => ({
         ...state,
         [action.searchText]: {
             ...state[action.searchText],
@@ -179,42 +181,42 @@ const TERM_SELECTOR = {
         },
     }),
 };
-const PAGE_SELECTOR = {
-    [GifTypes.REQUEST_SEARCH]: (state: {pages?} = {}) => {
+const PAGE_SELECTOR: Dictionary<Function> = {
+    [GifTypes.REQUEST_SEARCH]: (state: {pages?: any} = {}) => {
         if (typeof state.pages == 'undefined') {
             return {};
         }
         return {...state.pages};
     },
-    [GifTypes.RECEIVE_SEARCH]: (state, action) => ({
+    [GifTypes.RECEIVE_SEARCH]: (state: any, action: GenericAction) => ({
         ...state.pages,
-        [action.currentPage]: action.gfycats.map((gfycat) => gfycat.gfyId),
+        [action.currentPage]: action.gfycats.map((gfycat: any) => gfycat.gfyId),
     }),
 };
 
-const CACHE_SELECTORS = {
-    [GifTypes.CACHE_GIFS]: (state, action) => ({
+const CACHE_SELECTORS: Dictionary<Function> = {
+    [GifTypes.CACHE_GIFS]: (state: any, action: GenericAction) => ({
         ...state,
         gifs: CACHE_GIF_SELECTOR[action.type](state.gifs, action),
         updating: false,
     }),
-    [GifTypes.CACHE_REQUEST]: (state, action) => ({
+    [GifTypes.CACHE_REQUEST]: (state: any, action: GenericAction) => ({
         ...state,
         ...action.payload,
     }),
 };
 
-const CACHE_GIF_SELECTOR = {
-    [GifTypes.CACHE_GIFS]: (state, action) => ({
+const CACHE_GIF_SELECTOR: Dictionary<Function> = {
+    [GifTypes.CACHE_GIFS]: (state: any, action: GenericAction) => ({
         ...state,
-        ...action.gifs.reduce((map, obj) => {
+        ...action.gifs.reduce((map: any, obj: any) => {
             map[obj.gfyId] = obj;
             return map;
         }, {}),
     }),
 };
 
-function appReducer(state = {}, action) {
+function appReducer(state: any = {}, action: GenericAction) {
     const nextState = {...state};
     switch (action.type) {
     case GifTypes.SAVE_APP_PROPS:
@@ -224,17 +226,17 @@ function appReducer(state = {}, action) {
     }
 }
 
-function categoriesReducer(state = {}, action) {
+function categoriesReducer(state: any = {}, action: GenericAction) {
     const selector = CATEGORIES_SELECTORS[action.type];
     return selector ? selector(state, action) : state;
 }
 
-function searchReducer(state = {}, action) {
+function searchReducer(state: any = {}, action: GenericAction) {
     const selector = SEARCH_SELECTORS[action.type];
     return selector ? selector(state, action) : state;
 }
 
-function cacheReducer(state = {}, action) {
+function cacheReducer(state: any = {}, action: GenericAction) {
     const selector = CACHE_SELECTORS[action.type];
     return selector ? selector(state, action) : state;
 }
diff --git a/src/reducers/entities/groups.ts b/src/reducers/entities/groups.ts
index f83664bfb..ae073ba88 100644
--- a/src/reducers/entities/groups.ts
+++ b/src/reducers/entities/groups.ts
@@ -2,9 +2,13 @@
 // See LICENSE.txt for license information.
 import {combineReducers} from 'redux';
 import {GroupTypes} from 'action_types';
-import {GroupChannel, GroupSyncables, GroupTeam} from 'types/groups';
+import {GroupChannel, GroupSyncables, GroupTeam, Group} from 'types/groups';
+import {GenericAction} from 'types/actions';
+import {Team, TeamMembership} from 'types/teams';
+import {ChannelMembership} from 'types/channels';
+import {Dictionary} from 'types/utilities';
 
-function syncables(state = {}, action) {
+function syncables(state: Dictionary<GroupSyncables> = {}, action: GenericAction) {
     switch (action.type) {
     case GroupTypes.RECEIVED_GROUP_TEAMS: {
         return {
@@ -117,7 +121,7 @@ function syncables(state = {}, action) {
     }
 }
 
-function members(state = {}, action) {
+function members(state: any = {}, action: GenericAction) {
     switch (action.type) {
     case GroupTypes.RECEIVED_GROUP_MEMBERS: {
         return {
@@ -133,7 +137,7 @@ function members(state = {}, action) {
     }
 }
 
-function groups(state = {}, action) {
+function groups(state: Dictionary<Group> = {}, action: GenericAction) {
     switch (action.type) {
     case GroupTypes.RECEIVED_GROUP: {
         return {
diff --git a/src/reducers/entities/integrations.ts b/src/reducers/entities/integrations.ts
index cf017ac72..8dff4d445 100644
--- a/src/reducers/entities/integrations.ts
+++ b/src/reducers/entities/integrations.ts
@@ -3,8 +3,11 @@
 
 import {combineReducers} from 'redux';
 import {IntegrationTypes, UserTypes, ChannelTypes} from 'action_types';
+import {GenericAction} from 'types/actions';
+import {Command, IncomingWebhook, OutgoingWebhook, OAuthApp} from 'types/integrations';
+import {Dictionary, IDMappedObjects} from 'types/utilities';
 
-function incomingHooks(state = {}, action) {
+function incomingHooks(state: IDMappedObjects<IncomingWebhook> = {}, action: GenericAction) {
     switch (action.type) {
     case IntegrationTypes.RECEIVED_INCOMING_HOOK: {
         const nextState = {...state};
@@ -47,7 +50,7 @@ function incomingHooks(state = {}, action) {
     }
 }
 
-function outgoingHooks(state = {}, action) {
+function outgoingHooks(state: IDMappedObjects<OutgoingWebhook> = {}, action: GenericAction) {
     switch (action.type) {
     case IntegrationTypes.RECEIVED_OUTGOING_HOOK: {
         const nextState = {...state};
@@ -90,7 +93,7 @@ function outgoingHooks(state = {}, action) {
     }
 }
 
-function commands(state = {}, action) {
+function commands(state: IDMappedObjects<Command> = {}, action: GenericAction) {
     switch (action.type) {
     case IntegrationTypes.RECEIVED_COMMANDS:
     case IntegrationTypes.RECEIVED_CUSTOM_TEAM_COMMANDS: {
@@ -136,10 +139,10 @@ function commands(state = {}, action) {
     }
 }
 
-function systemCommands(state = {}, action) {
+function systemCommands(state: IDMappedObjects<Command> = {}, action: GenericAction) {
     switch (action.type) {
     case IntegrationTypes.RECEIVED_COMMANDS: {
-        const nextCommands = {};
+        const nextCommands: Dictionary<Command> = {};
         for (const command of action.data) {
             if (!command.id) {
                 nextCommands[command.trigger] = command;
@@ -164,7 +167,7 @@ function systemCommands(state = {}, action) {
     }
 }
 
-function oauthApps(state = {}, action) {
+function oauthApps(state: IDMappedObjects<OAuthApp> = {}, action: GenericAction) {
     switch (action.type) {
     case IntegrationTypes.RECEIVED_OAUTH_APPS: {
         const nextState = {...state};
@@ -191,7 +194,7 @@ function oauthApps(state = {}, action) {
     }
 }
 
-function dialogTriggerId(state = '', action) {
+function dialogTriggerId(state = '', action: GenericAction) {
     switch (action.type) {
     case IntegrationTypes.RECEIVED_DIALOG_TRIGGER_ID:
         return action.data;
@@ -200,7 +203,7 @@ function dialogTriggerId(state = '', action) {
     }
 }
 
-function dialog(state = '', action) {
+function dialog(state = '', action: GenericAction) {
     switch (action.type) {
     case IntegrationTypes.RECEIVED_DIALOG:
         return action.data;
diff --git a/src/reducers/entities/jobs.ts b/src/reducers/entities/jobs.ts
index 3bb8415cb..5357d2bf1 100644
--- a/src/reducers/entities/jobs.ts
+++ b/src/reducers/entities/jobs.ts
@@ -30,7 +30,7 @@ function jobsByTypeList(state: JobsByType = {}, action: GenericAction): JobsByTy
     case JobTypes.RECEIVED_JOBS_BY_TYPE: {
         const nextState = {...state};
         if (action.data && action.data.length && action.data.length > 0) {
-            nextState[action.data[0].type] = action.data;
+            nextState[action.data[0].type as JobType] = action.data;
         }
         return nextState;
     }
diff --git a/src/reducers/entities/plugins.ts b/src/reducers/entities/plugins.ts
index 69d2834b5..2875b7bd8 100644
--- a/src/reducers/entities/plugins.ts
+++ b/src/reducers/entities/plugins.ts
@@ -3,8 +3,9 @@
 
 import {combineReducers} from 'redux';
 import {PluginTypes} from 'action_types';
+import {GenericAction} from 'types/actions';
 
-function marketplacePlugins(state = [], action) {
+function marketplacePlugins(state = [], action: GenericAction) {
     switch (action.type) {
     case PluginTypes.RECEIVED_MARKETPLACE_PLUGINS: {
         return action.data ? action.data : [];
diff --git a/src/reducers/entities/posts.ts b/src/reducers/entities/posts.ts
index 107af1099..f5c0d8142 100644
--- a/src/reducers/entities/posts.ts
+++ b/src/reducers/entities/posts.ts
@@ -3,10 +3,12 @@
 import {ChannelTypes, GeneralTypes, PostTypes, UserTypes} from 'action_types';
 import {Posts} from '../../constants';
 import {comparePosts} from 'utils/post_utils';
-import {Post, PostsState} from 'types/posts';
-import {RelationOneToOne, Dictionary} from 'types/utilities';
+import {Post, PostsState, PostOrderBlock, MessageHistory} from 'types/posts';
+import {RelationOneToOne, Dictionary, IDMappedObjects, RelationOneToMany} from 'types/utilities';
+import {GenericAction} from 'types/actions';
+import {Reaction} from 'types/reactions';
 
-export function removeUnneededMetadata(post) {
+export function removeUnneededMetadata(post: Post) {
     if (!post.metadata) {
         return post;
     }
@@ -63,7 +65,7 @@ export function removeUnneededMetadata(post) {
     };
 }
 
-export function handlePosts(state: RelationOneToOne<Post, Post> = {}, action) {
+export function handlePosts(state: RelationOneToOne<Post, Post> = {}, action: GenericAction) {
     switch (action.type) {
     case PostTypes.RECEIVED_POST:
     case PostTypes.RECEIVED_NEW_POST: {
@@ -80,7 +82,7 @@ export function handlePosts(state: RelationOneToOne<Post, Post> = {}, action) {
     }
 
     case PostTypes.RECEIVED_POSTS: {
-        const posts = Object.values(action.data.posts);
+        const posts = Object.values(action.data.posts) as Post[];
 
         if (posts.length === 0) {
             return state;
@@ -184,7 +186,7 @@ export function handlePosts(state: RelationOneToOne<Post, Post> = {}, action) {
     }
 }
 
-function handlePostReceived(nextState, post) {
+function handlePostReceived(nextState: any, post: Post) {
     if (nextState[post.id] && nextState[post.id].update_at >= post.update_at) {
         // The stored post is newer than the one we've received
         return nextState;
@@ -212,7 +214,7 @@ function handlePostReceived(nextState, post) {
     return nextState;
 }
 
-export function handlePendingPosts(state: Array<string> = [], action) {
+export function handlePendingPosts(state: Array<string> = [], action: GenericAction) {
     switch (action.type) {
     case PostTypes.RECEIVED_NEW_POST: {
         const post = action.data;
@@ -278,10 +280,10 @@ export function handlePendingPosts(state: Array<string> = [], action) {
     }
 }
 
-export function postsInChannel(state = {}, action, prevPosts, nextPosts) {
+export function postsInChannel(state: Dictionary<Array<PostOrderBlock>> = {}, action: GenericAction, prevPosts: IDMappedObjects<Post>, nextPosts: Dictionary<Post>) {
     switch (action.type) {
     case PostTypes.RECEIVED_NEW_POST: {
-        const post = action.data;
+        const post = action.data as Post;
 
         const postsForChannel = state[post.channel_id];
         if (!postsForChannel) {
@@ -289,9 +291,9 @@ export function postsInChannel(state = {}, action, prevPosts, nextPosts) {
             return state;
         }
 
-        const recentBlockIndex = postsForChannel.findIndex((block) => block.recent);
+        const recentBlockIndex = postsForChannel.findIndex((block: PostOrderBlock) => block.recent);
 
-        let nextRecentBlock;
+        let nextRecentBlock: PostOrderBlock;
         if (recentBlockIndex === -1) {
             nextRecentBlock = {
                 order: [],
@@ -358,7 +360,7 @@ export function postsInChannel(state = {}, action, prevPosts, nextPosts) {
 
         const postsForChannel = state[post.channel_id] || [];
 
-        const recentBlockIndex = postsForChannel.findIndex((block) => block.recent);
+        const recentBlockIndex = postsForChannel.findIndex((block: PostOrderBlock) => block.recent);
         if (recentBlockIndex === -1) {
             // Nothing to do since there's no recent block and only the recent block should contain pending posts
             return state;
@@ -403,7 +405,7 @@ export function postsInChannel(state = {}, action, prevPosts, nextPosts) {
 
         if (recent) {
             // The newly received block is now the most recent, so unmark the current most recent block
-            const recentBlockIndex = postsForChannel.findIndex((block) => block.recent);
+            const recentBlockIndex = postsForChannel.findIndex((block: PostOrderBlock) => block.recent);
             if (recentBlockIndex !== -1) {
                 const recentBlock = postsForChannel[recentBlockIndex];
 
@@ -503,7 +505,7 @@ export function postsInChannel(state = {}, action, prevPosts, nextPosts) {
 
         const postsForChannel = state[action.channelId] || [];
 
-        const recentBlockIndex = postsForChannel.findIndex((block) => block.recent);
+        const recentBlockIndex = postsForChannel.findIndex((block: PostOrderBlock) => block.recent);
         if (recentBlockIndex === -1) {
             // Nothing to do since this shouldn't be dispatched if we haven't loaded the most recent posts yet
             return state;
@@ -513,7 +515,7 @@ export function postsInChannel(state = {}, action, prevPosts, nextPosts) {
 
         const mostOldestCreateAt = nextPosts[recentBlock.order[recentBlock.order.length - 1]].create_at;
 
-        const nextRecentBlock = {
+        const nextRecentBlock: PostOrderBlock = {
             ...recentBlock,
             order: [...recentBlock.order],
         };
@@ -576,7 +578,7 @@ export function postsInChannel(state = {}, action, prevPosts, nextPosts) {
             const block = nextPostsForChannel[i];
 
             // Remove any comments for this post
-            const nextOrder = block.order.filter((postId) => prevPosts[postId].root_id !== post.id);
+            const nextOrder = block.order.filter((postId: string) => prevPosts[postId].root_id !== post.id);
 
             if (nextOrder.length !== block.order.length) {
                 nextPostsForChannel[i] = {
@@ -618,7 +620,7 @@ export function postsInChannel(state = {}, action, prevPosts, nextPosts) {
         for (let i = 0; i < nextPostsForChannel.length; i++) {
             const block = nextPostsForChannel[i];
 
-            const nextOrder = block.order.filter((postId) => postId !== post.id && prevPosts[postId].root_id !== post.id);
+            const nextOrder = block.order.filter((postId: string) => postId !== post.id && prevPosts[postId].root_id !== post.id);
 
             if (nextOrder.length !== block.order.length) {
                 nextPostsForChannel[i] = {
@@ -672,11 +674,11 @@ export function postsInChannel(state = {}, action, prevPosts, nextPosts) {
     }
 }
 
-export function removeNonRecentEmptyPostBlocks(blocks) {
-    return blocks.filter((block) => block.order.length !== 0 || block.recent);
+export function removeNonRecentEmptyPostBlocks(blocks: PostOrderBlock[]) {
+    return blocks.filter((block: PostOrderBlock) => block.order.length !== 0 || block.recent);
 }
 
-export function mergePostBlocks(blocks, posts) {
+export function mergePostBlocks(blocks: PostOrderBlock[], posts: Dictionary<Post>) {
     let nextBlocks = [...blocks];
 
     // Remove any blocks that may have become empty by removing posts
@@ -733,7 +735,7 @@ export function mergePostBlocks(blocks, posts) {
     return nextBlocks;
 }
 
-export function mergePostOrder(left, right, posts) {
+export function mergePostOrder(left: string[], right: string[], posts: Dictionary<Post>) {
     const result = [...left];
 
     // Add without duplicates
@@ -757,7 +759,7 @@ export function mergePostOrder(left, right, posts) {
     return result;
 }
 
-export function postsInThread(state: Dictionary<string[]> = {}, action, prevPosts) {
+export function postsInThread(state: RelationOneToMany<Post, Post> = {}, action: GenericAction, prevPosts: Dictionary<Post>) {
     switch (action.type) {
     case PostTypes.RECEIVED_NEW_POST:
     case PostTypes.RECEIVED_POST: {
@@ -956,7 +958,7 @@ export function postsInThread(state: Dictionary<string[]> = {}, action, prevPost
     }
 }
 
-function selectedPostId(state = '', action) {
+function selectedPostId(state = '', action: GenericAction) {
     switch (action.type) {
     case PostTypes.RECEIVED_POST_SELECTED:
         return action.data;
@@ -967,7 +969,7 @@ function selectedPostId(state = '', action) {
     }
 }
 
-function currentFocusedPostId(state = '', action) {
+function currentFocusedPostId(state = '', action: GenericAction) {
     switch (action.type) {
     case PostTypes.RECEIVED_FOCUSED_POST:
         return action.data;
@@ -978,22 +980,22 @@ function currentFocusedPostId(state = '', action) {
     }
 }
 
-export function reactions(state = {}, action) {
+export function reactions(state: RelationOneToOne<Post, Dictionary<Reaction>> = {}, action: GenericAction) {
     switch (action.type) {
     case PostTypes.RECEIVED_REACTIONS: {
         const reactionsList = action.data;
-        const nextReactions = {};
-        reactionsList.forEach((reaction) => {
+        const nextReactions: Dictionary<Reaction> = {};
+        reactionsList.forEach((reaction: Reaction) => {
             nextReactions[reaction.user_id + '-' + reaction.emoji_name] = reaction;
         });
 
         return {
             ...state,
-            [action.postId]: nextReactions,
+            [action.postId!]: nextReactions,
         };
     }
     case PostTypes.RECEIVED_REACTION: {
-        const reaction = action.data;
+        const reaction = action.data as Reaction;
         const nextReactions = {...(state[reaction.post_id] || {})};
         nextReactions[reaction.user_id + '-' + reaction.emoji_name] = reaction;
 
@@ -1051,12 +1053,12 @@ export function reactions(state = {}, action) {
     }
 }
 
-function storeReactionsForPost(state, post) {
+function storeReactionsForPost(state: any, post: Post) {
     if (!post.metadata || !post.metadata.reactions || post.delete_at > 0) {
         return state;
     }
 
-    const reactionsForPost = {};
+    const reactionsForPost: Dictionary<Reaction> = {};
     if (post.metadata.reactions && post.metadata.reactions.length > 0) {
         for (const reaction of post.metadata.reactions) {
             reactionsForPost[reaction.user_id + '-' + reaction.emoji_name] = reaction;
@@ -1069,7 +1071,7 @@ function storeReactionsForPost(state, post) {
     };
 }
 
-export function openGraph(state = {}, action) {
+export function openGraph(state: RelationOneToOne<Post, any> = {}, action: GenericAction) {
     switch (action.type) {
     case PostTypes.RECEIVED_OPEN_GRAPH_METADATA: {
         const nextState = {...state};
@@ -1097,7 +1099,7 @@ export function openGraph(state = {}, action) {
     }
 }
 
-function storeOpenGraphForPost(state, post) {
+function storeOpenGraphForPost(state: any, post: Post) {
     if (!post.metadata || !post.metadata.embeds) {
         return state;
     }
@@ -1115,10 +1117,10 @@ function storeOpenGraphForPost(state, post) {
     }, state);
 }
 
-function messagesHistory(state: {messages?;index?} = {}, action) {
+function messagesHistory(state: Partial<MessageHistory> = {}, action: GenericAction) {
     switch (action.type) {
     case PostTypes.ADD_MESSAGE_INTO_HISTORY: {
-        const nextIndex = {};
+        const nextIndex: Dictionary<number> = {};
         let nextMessages = state.messages ? [...state.messages] : [];
         nextMessages.push(action.data);
         nextIndex[Posts.MESSAGE_TYPES.POST] = nextMessages.length;
@@ -1134,7 +1136,7 @@ function messagesHistory(state: {messages?;index?} = {}, action) {
         };
     }
     case PostTypes.RESET_HISTORY_INDEX: {
-        const index = {};
+        const index: Dictionary<number> = {};
         index[Posts.MESSAGE_TYPES.POST] = -1;
         index[Posts.MESSAGE_TYPES.COMMENT] = -1;
 
@@ -1147,7 +1149,7 @@ function messagesHistory(state: {messages?;index?} = {}, action) {
         };
     }
     case PostTypes.MOVE_HISTORY_INDEX_BACK: {
-        const index = {};
+        const index: Dictionary<number> = {};
         index[Posts.MESSAGE_TYPES.POST] = -1;
         index[Posts.MESSAGE_TYPES.COMMENT] = -1;
 
@@ -1161,7 +1163,7 @@ function messagesHistory(state: {messages?;index?} = {}, action) {
         };
     }
     case PostTypes.MOVE_HISTORY_INDEX_FORWARD: {
-        const index = {};
+        const index: Dictionary<number> = {};
         index[Posts.MESSAGE_TYPES.POST] = -1;
         index[Posts.MESSAGE_TYPES.COMMENT] = -1;
 
@@ -1176,7 +1178,7 @@ function messagesHistory(state: {messages?;index?} = {}, action) {
         };
     }
     case UserTypes.LOGOUT_SUCCESS: {
-        const index = {};
+        const index: Dictionary<number> = {};
         index[Posts.MESSAGE_TYPES.POST] = -1;
         index[Posts.MESSAGE_TYPES.COMMENT] = -1;
 
@@ -1190,7 +1192,7 @@ function messagesHistory(state: {messages?;index?} = {}, action) {
     }
 }
 
-export function expandedURLs(state = {}, action) {
+export function expandedURLs(state: Dictionary<string> = {}, action: GenericAction) {
     switch (action.type) {
     case GeneralTypes.REDIRECT_LOCATION_SUCCESS:
         return {
@@ -1207,9 +1209,9 @@ export function expandedURLs(state = {}, action) {
     }
 }
 
-export default function(state: Partial<PostsState> = {}, action) {
+export default function(state: Partial<PostsState> = {}, action: GenericAction) {
     const nextPosts = handlePosts(state.posts, action);
-    const nextPostsInChannel = postsInChannel(state.postsInChannel, action, state.posts, nextPosts);
+    const nextPostsInChannel = postsInChannel(state.postsInChannel, action, state.posts!, nextPosts);
 
     const nextState = {
 
@@ -1224,7 +1226,7 @@ export default function(state: Partial<PostsState> = {}, action) {
 
         // Object mapping post root ids to an array of posts ids of comments (but not the root post) in that thread
         // with no guaranteed order
-        postsInThread: postsInThread(state.postsInThread, action, state.posts),
+        postsInThread: postsInThread(state.postsInThread, action, state.posts!),
 
         // The current selected post
         selectedPostId: selectedPostId(state.selectedPostId, action),
diff --git a/src/reducers/entities/preferences.ts b/src/reducers/entities/preferences.ts
index f773e18a2..25c044494 100644
--- a/src/reducers/entities/preferences.ts
+++ b/src/reducers/entities/preferences.ts
@@ -3,15 +3,18 @@
 
 import {combineReducers} from 'redux';
 import {PreferenceTypes, UserTypes} from 'action_types';
+import {GenericAction} from 'types/actions';
+import {PreferenceType} from 'types/preferences';
+import {Dictionary} from 'types/utilities';
 
-function getKey(preference) {
+function getKey(preference: PreferenceType) {
     return `${preference.category}--${preference.name}`;
 }
 
-function myPreferences(state = {}, action) {
+function myPreferences(state: Dictionary<PreferenceType> = {}, action: GenericAction) {
     switch (action.type) {
     case PreferenceTypes.RECEIVED_ALL_PREFERENCES: {
-        const nextState = {};
+        const nextState: any = {};
 
         if (action.data) {
             for (const preference of action.data) {
diff --git a/src/reducers/entities/roles.ts b/src/reducers/entities/roles.ts
index 669872355..66e544d67 100644
--- a/src/reducers/entities/roles.ts
+++ b/src/reducers/entities/roles.ts
@@ -3,8 +3,11 @@
 
 import {combineReducers} from 'redux';
 import {RoleTypes, UserTypes} from 'action_types';
+import {GenericAction} from 'types/actions';
+import {Dictionary} from 'types/utilities';
+import {Role} from 'types/roles';
 
-function pending(state = new Set(), action) {
+function pending(state: Set<string> = new Set(), action: GenericAction) {
     switch (action.type) {
     case RoleTypes.SET_PENDING_ROLES:
         return action.data;
@@ -15,7 +18,7 @@ function pending(state = new Set(), action) {
     }
 }
 
-function roles(state = {}, action) {
+function roles(state: Dictionary<Role> = {}, action: GenericAction) {
     switch (action.type) {
     case RoleTypes.RECEIVED_ROLES: {
         if (action.data) {
diff --git a/src/reducers/entities/search.ts b/src/reducers/entities/search.ts
index b6b4394a7..7ae93090b 100644
--- a/src/reducers/entities/search.ts
+++ b/src/reducers/entities/search.ts
@@ -4,8 +4,12 @@ import {combineReducers} from 'redux';
 import {PostTypes, PreferenceTypes, SearchTypes, UserTypes} from 'action_types';
 import {Preferences} from '../../constants';
 import {PreferenceType} from 'types/preferences';
+import {GenericAction} from 'types/actions';
+import {Post} from 'types/posts';
+import {Dictionary} from 'types/utilities';
+import {Search} from 'types/search';
 
-function results(state: Array<string> = [], action) {
+function results(state: Array<string> = [], action: GenericAction) {
     switch (action.type) {
     case SearchTypes.RECEIVED_SEARCH_POSTS: {
         if (action.isGettingMore) {
@@ -32,7 +36,7 @@ function results(state: Array<string> = [], action) {
     }
 }
 
-function matches(state = {}, action) {
+function matches(state: Dictionary<Array<string>> = {}, action: GenericAction) {
     switch (action.type) {
     case SearchTypes.RECEIVED_SEARCH_POSTS:
         if (action.isGettingMore) {
@@ -57,7 +61,7 @@ function matches(state = {}, action) {
     }
 }
 
-function flagged(state: Array<string> = [], action) {
+function flagged(state: Array<string> = [], action: GenericAction) {
     switch (action.type) {
     case SearchTypes.RECEIVED_SEARCH_FLAGGED_POSTS: {
         return action.data.order;
@@ -76,7 +80,7 @@ function flagged(state: Array<string> = [], action) {
         if (action.data) {
             const nextState = [...state];
             let hasNewFlaggedPosts = false;
-            action.data.forEach((pref) => {
+            action.data.forEach((pref: PreferenceType) => {
                 if (pref.category === Preferences.CATEGORY_FLAGGED_POST) {
                     const exists = nextState.find((p) => p === pref.name);
                     if (!exists) {
@@ -119,7 +123,7 @@ function flagged(state: Array<string> = [], action) {
     }
 }
 
-function removePinnedPost(state, post) {
+function removePinnedPost(state: Dictionary<Array<string>>, post: Post) {
     if (post && state[post.channel_id]) {
         const postId = post.id;
         const channelId = post.channel_id;
@@ -138,7 +142,7 @@ function removePinnedPost(state, post) {
     return state;
 }
 
-function pinned(state = {}, action) {
+function pinned(state: Dictionary<Array<string>> = {}, action: GenericAction) {
     switch (action.type) {
     case SearchTypes.RECEIVED_SEARCH_PINNED_POSTS: {
         const {channelId, pinned: posts} = action.data;
@@ -191,7 +195,7 @@ function pinned(state = {}, action) {
     }
 }
 
-function recent(state = {}, action) {
+function recent(state: Dictionary<Array<Search>> = {}, action: GenericAction) {
     const {data, type} = action;
 
     switch (type) {
@@ -236,7 +240,7 @@ function recent(state = {}, action) {
     }
 }
 
-function current(state = {}, action) {
+function current(state: any = {}, action: GenericAction) {
     const {data, type} = action;
     switch (type) {
     case SearchTypes.RECEIVED_SEARCH_TERM: {
@@ -258,7 +262,7 @@ function current(state = {}, action) {
     }
 }
 
-function isSearchingTerm(state = false, action) {
+function isSearchingTerm(state = false, action: GenericAction) {
     switch (action.type) {
     case SearchTypes.SEARCH_POSTS_REQUEST:
         return !action.isGettingMore;
@@ -270,7 +274,7 @@ function isSearchingTerm(state = false, action) {
     }
 }
 
-function isSearchGettingMore(state = false, action) {
+function isSearchGettingMore(state = false, action: GenericAction) {
     switch (action.type) {
     case SearchTypes.SEARCH_POSTS_REQUEST:
         return action.isGettingMore;
diff --git a/src/reducers/entities/teams.ts b/src/reducers/entities/teams.ts
index fee222b26..eb45547c9 100644
--- a/src/reducers/entities/teams.ts
+++ b/src/reducers/entities/teams.ts
@@ -297,7 +297,7 @@ function membersInTeam(state: RelationOneToOne<Team, RelationOneToOne<UserProfil
     }
 }
 
-function stats(state = {}, action: GenericAction) {
+function stats(state: any = {}, action: GenericAction) {
     switch (action.type) {
     case TeamTypes.RECEIVED_TEAM_STATS: {
         const stat = action.data;
diff --git a/src/reducers/entities/typing.ts b/src/reducers/entities/typing.ts
index 8d2893051..84a2c23a4 100644
--- a/src/reducers/entities/typing.ts
+++ b/src/reducers/entities/typing.ts
@@ -37,7 +37,7 @@ export default function typing(state: Typing = {}, action: GenericAction): Typin
         } = data;
 
         if (state[id] && state[id][userId] <= now) {
-            const nextState = {
+            const nextState: Typing = {
                 ...state,
                 [id]: {...state[id]},
             };
diff --git a/src/reducers/entities/users.ts b/src/reducers/entities/users.ts
index d4a03a420..ea573da6f 100644
--- a/src/reducers/entities/users.ts
+++ b/src/reducers/entities/users.ts
@@ -4,8 +4,13 @@
 import {combineReducers} from 'redux';
 import {UserTypes, ChannelTypes} from 'action_types';
 import {profileListToMap} from 'utils/user_utils';
+import {GenericAction} from 'types/actions';
+import {UserProfile} from 'types/users';
+import {RelationOneToMany, IDMappedObjects, RelationOneToOne} from 'types/utilities';
+import {Team} from 'types/teams';
+import {Channel} from 'types/channels';
 
-function profilesToSet(state, action) {
+function profilesToSet(state: RelationOneToMany<Team, UserProfile>, action: GenericAction) {
     const id = action.id;
     const nextSet = new Set(state[id]);
     Object.keys(action.data).forEach((key) => {
@@ -18,11 +23,11 @@ function profilesToSet(state, action) {
     };
 }
 
-function profileListToSet(state, action, replace = false) {
+function profileListToSet(state: RelationOneToMany<Team, UserProfile>, action: GenericAction, replace = false) {
     const id = action.id;
     const nextSet = replace ? new Set() : new Set(state[id]);
     if (action.data) {
-        action.data.forEach((profile) => {
+        action.data.forEach((profile: UserProfile) => {
             nextSet.add(profile.id);
         });
 
@@ -35,11 +40,11 @@ function profileListToSet(state, action, replace = false) {
     return state;
 }
 
-function removeProfileListFromSet(state, action) {
+function removeProfileListFromSet(state: RelationOneToMany<Team, UserProfile>, action: GenericAction) {
     const id = action.id;
     const nextSet = new Set(state[id]);
     if (action.data) {
-        action.data.forEach((profile) => {
+        action.data.forEach((profile: UserProfile) => {
             nextSet.delete(profile.id);
         });
 
@@ -52,7 +57,7 @@ function removeProfileListFromSet(state, action) {
     return state;
 }
 
-function addProfileToSet(state, action) {
+function addProfileToSet(state: RelationOneToMany<Team, UserProfile>, action: GenericAction) {
     const {id, user_id: userId} = action.data;
     const nextSet = new Set(state[id]);
     nextSet.add(userId);
@@ -62,7 +67,7 @@ function addProfileToSet(state, action) {
     };
 }
 
-function removeProfileFromSet(state, action) {
+function removeProfileFromSet(state: RelationOneToMany<Team, UserProfile>, action: GenericAction) {
     const {id, user_id: userId} = action.data;
     const nextSet = new Set(state[id]);
     nextSet.delete(userId);
@@ -72,7 +77,7 @@ function removeProfileFromSet(state, action) {
     };
 }
 
-function currentUserId(state = '', action) {
+function currentUserId(state = '', action: GenericAction) {
     switch (action.type) {
     case UserTypes.RECEIVED_ME: {
         const data = action.data || action.payload;
@@ -87,7 +92,7 @@ function currentUserId(state = '', action) {
     return state;
 }
 
-function mySessions(state: Array<{id}> = [], action) {
+function mySessions(state: Array<{id: string}> = [], action: GenericAction) {
     switch (action.type) {
     case UserTypes.RECEIVED_SESSIONS:
         return [...action.data];
@@ -125,7 +130,7 @@ function mySessions(state: Array<{id}> = [], action) {
     }
 }
 
-function myAudits(state = [], action) {
+function myAudits(state = [], action: GenericAction) {
     switch (action.type) {
     case UserTypes.RECEIVED_AUDITS:
         return [...action.data];
@@ -138,7 +143,7 @@ function myAudits(state = [], action) {
     }
 }
 
-function profiles(state = {}, action) {
+function profiles(state: IDMappedObjects<UserProfile> = {}, action: GenericAction) {
     switch (action.type) {
     case UserTypes.RECEIVED_ME:
     case UserTypes.RECEIVED_PROFILE: {
@@ -179,7 +184,7 @@ function profiles(state = {}, action) {
     }
 }
 
-function profilesInTeam(state = {}, action) {
+function profilesInTeam(state: RelationOneToMany<Team, UserProfile> = {}, action: GenericAction) {
     switch (action.type) {
     case UserTypes.RECEIVED_PROFILE_IN_TEAM:
         return addProfileToSet(state, action);
@@ -204,7 +209,7 @@ function profilesInTeam(state = {}, action) {
     }
 }
 
-function profilesNotInTeam(state = {}, action) {
+function profilesNotInTeam(state: RelationOneToMany<Team, UserProfile> = {}, action: GenericAction) {
     switch (action.type) {
     case UserTypes.RECEIVED_PROFILE_NOT_IN_TEAM:
         return addProfileToSet(state, action);
@@ -229,16 +234,16 @@ function profilesNotInTeam(state = {}, action) {
     }
 }
 
-function profilesWithoutTeam(state = new Set(), action) {
+function profilesWithoutTeam(state: Set<string> = new Set(), action: GenericAction) {
     switch (action.type) {
     case UserTypes.RECEIVED_PROFILE_WITHOUT_TEAM: {
         const nextSet = new Set(state);
-        Object.values(action.data).forEach((id) => nextSet.add(id));
+        Object.values(action.data).forEach((id: string) => nextSet.add(id));
         return nextSet;
     }
     case UserTypes.RECEIVED_PROFILES_LIST_WITHOUT_TEAM: {
         const nextSet = new Set(state);
-        action.data.forEach((user) => nextSet.add(user.id));
+        action.data.forEach((user: UserProfile) => nextSet.add(user.id));
         return nextSet;
     }
     case UserTypes.RECEIVED_PROFILE_IN_TEAM: {
@@ -254,7 +259,7 @@ function profilesWithoutTeam(state = new Set(), action) {
     }
 }
 
-function profilesInChannel(state = {}, action) {
+function profilesInChannel(state: RelationOneToMany<Channel, UserProfile> = {}, action: GenericAction) {
     switch (action.type) {
     case UserTypes.RECEIVED_PROFILE_IN_CHANNEL:
         return addProfileToSet(state, action);
@@ -269,10 +274,12 @@ function profilesInChannel(state = {}, action) {
         return removeProfileFromSet(state, action);
 
     case ChannelTypes.CHANNEL_MEMBER_REMOVED:
-        return removeProfileFromSet(state, {data: {
-            id: action.data.channel_id,
-            user_id: action.data.user_id,
-        }});
+        return removeProfileFromSet(state, {
+            type: '',
+            data: {
+                id: action.data.channel_id,
+                user_id: action.data.user_id,
+            }});
 
     case UserTypes.LOGOUT_SUCCESS:
         return {};
@@ -282,7 +289,7 @@ function profilesInChannel(state = {}, action) {
     }
 }
 
-function profilesNotInChannel(state = {}, action) {
+function profilesNotInChannel(state: RelationOneToMany<Channel, UserProfile> = {}, action: GenericAction) {
     switch (action.type) {
     case UserTypes.RECEIVED_PROFILE_NOT_IN_CHANNEL:
         return addProfileToSet(state, action);
@@ -300,10 +307,12 @@ function profilesNotInChannel(state = {}, action) {
         return removeProfileFromSet(state, action);
 
     case ChannelTypes.CHANNEL_MEMBER_ADDED:
-        return removeProfileFromSet(state, {data: {
-            id: action.data.channel_id,
-            user_id: action.data.user_id,
-        }});
+        return removeProfileFromSet(state, {
+            type: '',
+            data: {
+                id: action.data.channel_id,
+                user_id: action.data.user_id,
+            }});
 
     case UserTypes.LOGOUT_SUCCESS:
         return {};
@@ -313,7 +322,7 @@ function profilesNotInChannel(state = {}, action) {
     }
 }
 
-function statuses(state = {}, action) {
+function statuses(state: RelationOneToOne<UserProfile, string> = {}, action: GenericAction) {
     switch (action.type) {
     case UserTypes.RECEIVED_STATUS: {
         const nextState = Object.assign({}, state);
@@ -338,7 +347,7 @@ function statuses(state = {}, action) {
     }
 }
 
-function myUserAccessTokens(state = {}, action) {
+function myUserAccessTokens(state: any = {}, action: GenericAction) {
     switch (action.type) {
     case UserTypes.RECEIVED_MY_USER_ACCESS_TOKEN: {
         const nextState = {...state};
@@ -389,7 +398,7 @@ function myUserAccessTokens(state = {}, action) {
     }
 }
 
-function stats(state = {}, action) {
+function stats(state = {}, action: GenericAction) {
     switch (action.type) {
     case UserTypes.RECEIVED_USER_STATS: {
         const stat = action.data;
diff --git a/src/reducers/errors/index.ts b/src/reducers/errors/index.ts
index ba47c9a6e..20cd493ae 100644
--- a/src/reducers/errors/index.ts
+++ b/src/reducers/errors/index.ts
@@ -1,11 +1,12 @@
 // Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
 // See LICENSE.txt for license information.
 import {ErrorTypes} from 'action_types';
-export default ((state: Array<{error;displayable;date}> = [], action) => {
+import {GenericAction} from 'types/actions';
+export default ((state: Array<{error: any;displayable?: boolean;date: string}> = [], action: GenericAction) => {
     switch (action.type) {
     case ErrorTypes.DISMISS_ERROR: {
         const nextState = [...state];
-        nextState.splice(action.index, 1);
+        nextState.splice(action.index!, 1);
 
         return nextState;
     }
diff --git a/src/reducers/websocket.ts b/src/reducers/websocket.ts
index 96d39ab76..89eaba5a3 100644
--- a/src/reducers/websocket.ts
+++ b/src/reducers/websocket.ts
@@ -2,6 +2,7 @@
 // See LICENSE.txt for license information.
 
 import {GeneralTypes, UserTypes} from 'action_types';
+import {GenericAction} from 'types/actions';
 
 function getInitialState() {
     return {
@@ -11,7 +12,7 @@ function getInitialState() {
     };
 }
 
-export default function(state = getInitialState(), action) {
+export default function(state = getInitialState(), action: GenericAction) {
     if (!state.connected && action.type === GeneralTypes.WEBSOCKET_SUCCESS) {
         return {
             ...state,
diff --git a/src/selectors/entities/admin.ts b/src/selectors/entities/admin.ts
index 27130d876..1df751d81 100644
--- a/src/selectors/entities/admin.ts
+++ b/src/selectors/entities/admin.ts
@@ -1,38 +1,40 @@
 // Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
 // See LICENSE.txt for license information.
 
-export function getLogs(state) {
+import {GlobalState} from 'types/store';
+
+export function getLogs(state: GlobalState) {
     return state.entities.admin.logs;
 }
 
-export function getAudits(state) {
+export function getAudits(state: GlobalState) {
     return state.entities.admin.audits;
 }
 
-export function getConfig(state) {
+export function getConfig(state: GlobalState) {
     return state.entities.admin.config;
 }
 
-export function getLdapGroups(state) {
+export function getLdapGroups(state: GlobalState) {
     return state.entities.admin.ldapGroups;
 }
 
-export function getLdapGroupsCount(state) {
+export function getLdapGroupsCount(state: GlobalState) {
     return state.entities.admin.ldapGroupsCount;
 }
 
-export function getEnvironmentConfig(state) {
+export function getEnvironmentConfig(state: GlobalState) {
     return state.entities.admin.environmentConfig;
 }
 
-export function getComplianceReports(state) {
+export function getComplianceReports(state: GlobalState) {
     return state.entities.admin.complianceReports;
 }
 
-export function getClusterInfo(state) {
+export function getClusterInfo(state: GlobalState) {
     return state.entities.admin.clusterInfo;
 }
 
-export function getUserAccessTokens(state) {
+export function getUserAccessTokens(state: GlobalState) {
     return state.entities.admin.userAccessTokens;
 }
diff --git a/src/selectors/entities/bots.ts b/src/selectors/entities/bots.ts
index cdff854c4..40fcd6913 100644
--- a/src/selectors/entities/bots.ts
+++ b/src/selectors/entities/bots.ts
@@ -1,6 +1,8 @@
 // Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
 // See LICENSE.txt for license information.
 
-export function getBotAccounts(state) {
+import {GlobalState} from 'types/store';
+
+export function getBotAccounts(state: GlobalState) {
     return state.entities.bots.accounts;
 }
diff --git a/src/selectors/entities/channels.ts b/src/selectors/entities/channels.ts
index 7007282e5..005dbb6be 100644
--- a/src/selectors/entities/channels.ts
+++ b/src/selectors/entities/channels.ts
@@ -22,7 +22,9 @@ import {TeamMembership, Team} from 'types/teams';
 import {NameMappedObjects, UserIDMappedObjects, IDMappedObjects, RelationOneToOne, RelationOneToMany} from 'types/utilities';
 
 import {getUserIdsInChannels} from './users';
+import {Config} from 'types/config';
 type SortingType = 'recent' | 'alpha';
+
 export function getAllChannels(state: GlobalState): IDMappedObjects<Channel> {
     return state.entities.channels.channels;
 }
@@ -42,7 +44,7 @@ export function getChannelMembersInChannels(state: GlobalState): RelationOneToOn
     return state.entities.channels.membersInChannel;
 }
 
-function sortChannelsByRecencyOrAlpha(locale, lastPosts, sorting: SortingType, a, b) {
+function sortChannelsByRecencyOrAlpha(locale: string, lastPosts: RelationOneToOne<Channel, Post>, sorting: SortingType, a: Channel, b: Channel) {
     if (sorting === 'recent') {
         return sortChannelsByRecency(lastPosts, a, b);
     }
@@ -110,11 +112,11 @@ export function filterChannels(unreadIds: Array<string>, favoriteIds: Array<stri
 export function makeGetChannel(): (b: GlobalState, a: {
     id: string;
 }) => Channel {
-    return createSelector(getAllChannels, (state: GlobalState, props) => props.id, (state: GlobalState) => state.entities.users, getTeammateNameDisplaySetting, (allChannels, channelId, users, teammateNameDisplay) => {
+    return createSelector(getAllChannels, (state: GlobalState, props: {id: string}) => props.id, (state: GlobalState) => state.entities.users, getTeammateNameDisplaySetting, (allChannels, channelId, users, teammateNameDisplay) => {
         const channel = allChannels[channelId];
 
         if (channel) {
-            return completeDirectChannelInfo(users, teammateNameDisplay, channel);
+            return completeDirectChannelInfo(users, teammateNameDisplay!, channel);
         }
 
         return channel;
@@ -203,32 +205,36 @@ export const getChannelsInCurrentTeam: (a: GlobalState) => Array<Channel> = crea
 
     return sortAndInjectChannels(channels, currentTeamChannelSet, locale);
 });
+
 export const getChannelsNameMapInTeam: (b: GlobalState, a: string) => NameMappedObjects<Channel> = createSelector(getAllChannels, getChannelsInTeam, (state: GlobalState, teamId: string): string => teamId, (channels: IDMappedObjects<Channel>, channelsInTeams: RelationOneToMany<Team, Channel>, teamId: string): NameMappedObjects<Channel> => {
     const channelsInTeam = channelsInTeams[teamId] || [];
-    const channelMap = {};
+    const channelMap: NameMappedObjects<Channel> = {};
     channelsInTeam.forEach((id) => {
         const channel = channels[id];
         channelMap[channel.name] = channel;
     });
     return channelMap;
 });
+
 export const getChannelsNameMapInCurrentTeam: (a: GlobalState) => NameMappedObjects<Channel> = createSelector(getAllChannels, getChannelSetInCurrentTeam, (channels: IDMappedObjects<Channel>, currentTeamChannelSet: Array<string>): NameMappedObjects<Channel> => {
-    const channelMap = {};
+    const channelMap: NameMappedObjects<Channel> = {};
     currentTeamChannelSet.forEach((id) => {
         const channel = channels[id];
         channelMap[channel.name] = channel;
     });
     return channelMap;
-}); // Returns both DMs and GMs
+});
 
+// Returns both DMs and GMs
 export const getAllDirectChannels: (a: GlobalState) => Array<Channel> = createSelector(getAllChannels, getDirectChannelsSet, (state: GlobalState): UsersState => state.entities.users, getTeammateNameDisplaySetting, (channels: IDMappedObjects<Channel>, channelSet: Set<string>, users: UsersState, teammateNameDisplay: string): Array<Channel> => {
     const dmChannels: Channel[] = [];
     channelSet.forEach((c) => {
         dmChannels.push(completeDirectChannelInfo(users, teammateNameDisplay, channels[c]));
     });
     return dmChannels;
-}); // Returns only GMs
+});
 
+// Returns only GMs
 export const getGroupChannels: (a: GlobalState) => Array<Channel> = createSelector(getAllChannels, getDirectChannelsSet, (state: GlobalState): UsersState => state.entities.users, getTeammateNameDisplaySetting, (channels: IDMappedObjects<Channel>, channelSet: Set<string>, users: UsersState, teammateNameDisplay: string): Array<Channel> => {
     const gmChannels: Channel[] = [];
     channelSet.forEach((id) => {
@@ -240,21 +246,25 @@ export const getGroupChannels: (a: GlobalState) => Array<Channel> = createSelect
     });
     return gmChannels;
 });
+
 export const getMyChannels: (a: GlobalState) => Array<Channel> = createSelector(getChannelsInCurrentTeam, getAllDirectChannels, getMyChannelMemberships, (channels: Array<Channel>, directChannels: Array<Channel>, myMembers: RelationOneToOne<Channel, ChannelMembership>): Array<Channel> => {
     return [...channels, ...directChannels].filter((c) => myMembers.hasOwnProperty(c.id));
 });
+
 export const getOtherChannels: (b: GlobalState, a?: boolean | null) => Array<Channel> = createSelector(getChannelsInCurrentTeam, getMyChannelMemberships, (state: GlobalState, archived: boolean | undefined | null = true) => archived, (channels: Array<Channel>, myMembers: RelationOneToOne<Channel, ChannelMembership>, archived?: boolean | null): Array<Channel> => {
     return channels.filter((c) => !myMembers.hasOwnProperty(c.id) && c.type === General.OPEN_CHANNEL && (archived ? true : c.delete_at === 0));
 });
+
 export const getArchivedChannels: (a: GlobalState) => Array<Channel> = createSelector(getChannelsInCurrentTeam, getMyChannelMemberships, (channels: Array<Channel>, myMembers: RelationOneToOne<Channel, ChannelMembership>): Array<Channel> => {
     return channels.filter((c) => myMembers.hasOwnProperty(c.id) && c.delete_at !== 0);
 });
+
 export const getChannelsByCategory: (a: GlobalState) => {
     favoriteChannels: Array<Channel>;
     publicChannels: Array<Channel>;
     privateChannels: Array<Channel>;
     directAndGroupChannels: Array<Channel>;
-} = createSelector(getCurrentChannelId, getMyChannels, getMyChannelMemberships, getConfig, getMyPreferences, getTeammateNameDisplaySetting, (state: GlobalState): UsersState => state.entities.users, getLastPostPerChannel, (currentChannelId: string, channels: Array<Channel>, myMembers: RelationOneToOne<Channel, ChannelMembership>, config: any, myPreferences: {
+} = createSelector(getCurrentChannelId, getMyChannels, getMyChannelMemberships, getConfig, getMyPreferences, getTeammateNameDisplaySetting, (state: GlobalState): UsersState => state.entities.users, getLastPostPerChannel, (currentChannelId: string, channels: Array<Channel>, myMembers: RelationOneToOne<Channel, ChannelMembership>, config: Config, myPreferences: {
     [x: string]: PreferenceType;
 }, teammateNameDisplay: string, usersState: UsersState, lastPosts: RelationOneToOne<Channel, Post>) => {
     const allChannels = channels.map((c) => {
@@ -265,13 +275,14 @@ export const getChannelsByCategory: (a: GlobalState) => {
     });
     return buildDisplayableChannelList(usersState, allChannels, myMembers, config, myPreferences, teammateNameDisplay, lastPosts);
 });
+
 export const getChannelsWithUnreadSection: (a: GlobalState) => {
     unreadChannels: Array<Channel>;
     favoriteChannels: Array<Channel>;
     publicChannels: Array<Channel>;
     privateChannels: Array<Channel>;
     directAndGroupChannels: Array<Channel>;
-} = createSelector(getCurrentChannelId, getMyChannels, getMyChannelMemberships, getConfig, getMyPreferences, getTeammateNameDisplaySetting, (state: GlobalState): UsersState => state.entities.users, getLastPostPerChannel, (currentChannelId: string, channels: Array<Channel>, myMembers: RelationOneToOne<Channel, ChannelMembership>, config: any, myPreferences: {
+} = createSelector(getCurrentChannelId, getMyChannels, getMyChannelMemberships, getConfig, getMyPreferences, getTeammateNameDisplaySetting, (state: GlobalState): UsersState => state.entities.users, getLastPostPerChannel, (currentChannelId: string, channels: Array<Channel>, myMembers: RelationOneToOne<Channel, ChannelMembership>, config: Config, myPreferences: {
     [x: string]: PreferenceType;
 }, teammateNameDisplay: string, usersState: UsersState, lastPosts: RelationOneToOne<Channel, Post>) => {
     const allChannels = channels.map((c) => {
@@ -282,12 +293,15 @@ export const getChannelsWithUnreadSection: (a: GlobalState) => {
     });
     return buildDisplayableChannelListWithUnreadSection(usersState, allChannels, myMembers, config, myPreferences, teammateNameDisplay, lastPosts);
 });
+
 export const getDefaultChannel: (a: GlobalState) => Channel | undefined | null = createSelector(getAllChannels, getCurrentTeamId, (channels: IDMappedObjects<Channel>, teamId: string): Channel | undefined | null => {
     return Object.keys(channels).map((key) => channels[key]).find((c) => c && c.team_id === teamId && c.name === General.DEFAULT_CHANNEL);
 });
+
 export const getMembersInCurrentChannel: (a: GlobalState) => UserIDMappedObjects<ChannelMembership> = createSelector(getCurrentChannelId, getChannelMembersInChannels, (currentChannelId: string, members: RelationOneToOne<Channel, UserIDMappedObjects<ChannelMembership>>): UserIDMappedObjects<ChannelMembership> => {
     return members[currentChannelId];
 });
+
 export const getUnreads: (a: GlobalState) => {
     messageCount: number;
     mentionCount: number;
@@ -392,7 +406,7 @@ export const canManageChannelMembers: (a: GlobalState) => boolean = createSelect
     permission: Permissions.MANAGE_PRIVATE_CHANNEL_MEMBERS,
 }), (state: GlobalState): boolean => haveICurrentChannelPermission(state, {
     permission: Permissions.MANAGE_PUBLIC_CHANNEL_MEMBERS,
-}), (channel: Channel, user: UserProfile, teamMembership: TeamMembership, channelMembership: ChannelMembership | undefined | null, config: any, license: any, newPermissions: boolean, managePrivateMembers: boolean, managePublicMembers: boolean): boolean => {
+}), (channel: Channel, user: UserProfile, teamMembership: TeamMembership, channelMembership: ChannelMembership | undefined | null, config: Config, license: any, newPermissions: boolean, managePrivateMembers: boolean, managePublicMembers: boolean): boolean => {
     if (!channel) {
         return false;
     }
@@ -490,21 +504,21 @@ export const getUnreadChannels: (b: GlobalState, a?: Channel | null) => Array<Ch
         const c = channels[id];
 
         if (c.type === General.DM_CHANNEL || c.type === General.GM_CHANNEL) {
-            return completeDirectChannelDisplayName(currentUser.id, profiles, userIdsInChannels[id], settings, c);
+            return completeDirectChannelDisplayName(currentUser.id, profiles, userIdsInChannels[id], settings!, c);
         }
 
         return c;
     });
     return allUnreadChannels;
 });
-export const getMapAndSortedUnreadChannelIds: (c: GlobalState, b: Channel, a: SortingType) => Array<string> = createIdsSelector(getUnreadChannels, getCurrentUser, getMyChannelMemberships, getLastPostPerChannel, (state, lastUnreadChannel, sorting: SortingType = 'alpha') => sorting, (channels, currentUser, myMembers, lastPosts: RelationOneToOne<Channel, Post>, sorting: SortingType) => {
+export const getMapAndSortedUnreadChannelIds: (c: GlobalState, b: Channel, a: SortingType) => Array<string> = createIdsSelector(getUnreadChannels, getCurrentUser, getMyChannelMemberships, getLastPostPerChannel, (state: GlobalState, lastUnreadChannel: Channel, sorting: SortingType = 'alpha') => sorting, (channels, currentUser, myMembers, lastPosts: RelationOneToOne<Channel, Post>, sorting: SortingType) => {
     return mapAndSortChannelIds(channels, currentUser, myMembers, lastPosts, sorting, true);
 });
-export const getSortedUnreadChannelIds: (e: GlobalState, d: Channel|null, c: boolean, b: boolean, a: SortingType) => Array<string> = createIdsSelector(getUnreadChannelIds, (state, lastUnreadChannel, unreadsAtTop, favoritesAtTop, sorting: SortingType = 'alpha') => {
+export const getSortedUnreadChannelIds: (e: GlobalState, d: Channel|null, c: boolean, b: boolean, a: SortingType) => Array<string> = createIdsSelector(getUnreadChannelIds, (state: GlobalState, lastUnreadChannel: Channel, unreadsAtTop: boolean, favoritesAtTop: boolean, sorting: SortingType = 'alpha') => {
     return getMapAndSortedUnreadChannelIds(state, lastUnreadChannel, sorting);
 }, (unreadChannelIds, mappedAndSortedUnreadChannelIds) => mappedAndSortedUnreadChannelIds); // Favorites
 
-export const getFavoriteChannels: (a: GlobalState) => Array<Channel> = createIdsSelector(getCurrentUser, getUsers, getUserIdsInChannels, getAllChannels, getMyChannelMemberships, getFavoritesPreferences, getChannelIdsForCurrentTeam, getTeammateNameDisplaySetting, getConfig, getMyPreferences, getCurrentChannelId, (currentUser: UserProfile, profiles: IDMappedObjects<UserProfile>, userIdsInChannels: any, channels: IDMappedObjects<Channel>, myMembers: RelationOneToOne<Channel, ChannelMembership>, favoriteIds: Array<string>, teamChannelIds: Array<string>, settings: string, config: any, prefs: {
+export const getFavoriteChannels: (a: GlobalState) => Array<Channel> = createIdsSelector(getCurrentUser, getUsers, getUserIdsInChannels, getAllChannels, getMyChannelMemberships, getFavoritesPreferences, getChannelIdsForCurrentTeam, getTeammateNameDisplaySetting, getConfig, getMyPreferences, getCurrentChannelId, (currentUser: UserProfile, profiles: IDMappedObjects<UserProfile>, userIdsInChannels: any, channels: IDMappedObjects<Channel>, myMembers: RelationOneToOne<Channel, ChannelMembership>, favoriteIds: Array<string>, teamChannelIds: Array<string>, settings: string, config: Config, prefs: {
     [x: string]: PreferenceType;
 }, currentChannelId: string): Array<Channel> => {
     if (!currentUser) {
@@ -547,11 +561,14 @@ export const getFavoriteChannels: (a: GlobalState) => Array<Channel> = createIds
     });
     return favoriteChannel;
 });
-export const getFavoriteChannelIds: (e: GlobalState, d: Channel, c: boolean, b: boolean, a: SortingType) => Array<string> = createIdsSelector(getFavoriteChannels, getCurrentUser, getMyChannelMemberships, getLastPostPerChannel, (state, lastUnreadChannel, unreadsAtTop, favoritesAtTop, sorting: SortingType = 'alpha') => sorting, mapAndSortChannelIds);
-export const getSortedFavoriteChannelIds: (e: GlobalState, d: Channel|null, c: boolean, b: boolean, a: SortingType) => Array<string> = createIdsSelector(getUnreadChannelIds, getFavoritesPreferences, (state, lastUnreadChannel, unreadsAtTop, favoritesAtTop, sorting: SortingType) => getFavoriteChannelIds(state, lastUnreadChannel, unreadsAtTop, favoritesAtTop, sorting), (state, lastUnreadChannel, unreadsAtTop = true) => unreadsAtTop, (unreadChannelIds, favoritePreferences, favoriteChannelIds, unreadsAtTop) => {
+
+export const getFavoriteChannelIds: (e: GlobalState, d: Channel, c: boolean, b: boolean, a: SortingType) => Array<string> = createIdsSelector(getFavoriteChannels, getCurrentUser, getMyChannelMemberships, getLastPostPerChannel, (state: GlobalState, lastUnreadChannel: Channel, unreadsAtTop: boolean, favoritesAtTop: boolean, sorting: SortingType = 'alpha') => sorting, mapAndSortChannelIds);
+
+export const getSortedFavoriteChannelIds: (e: GlobalState, d: Channel | null, c: boolean, b: boolean, a: SortingType) => Array<string> = createIdsSelector(getUnreadChannelIds, getFavoritesPreferences, (state: GlobalState, lastUnreadChannel: Channel, unreadsAtTop: boolean, favoritesAtTop: boolean, sorting: SortingType) => getFavoriteChannelIds(state, lastUnreadChannel, unreadsAtTop, favoritesAtTop, sorting), (state, lastUnreadChannel, unreadsAtTop = true) => unreadsAtTop, (unreadChannelIds, favoritePreferences, favoriteChannelIds, unreadsAtTop) => {
     return filterChannels(unreadChannelIds, favoritePreferences, favoriteChannelIds, unreadsAtTop, false);
-}); // Public Channels
+});
 
+// Public Channels
 export const getPublicChannels: (a: GlobalState) => Array<Channel> = createSelector(getCurrentUser, getAllChannels, getMyChannelMemberships, getChannelIdsForCurrentTeam, (currentUser, channels, myMembers, teamChannelIds) => {
     if (!currentUser) {
         return [];
@@ -567,8 +584,10 @@ export const getPublicChannels: (a: GlobalState) => Array<Channel> = createSelec
     }).map((id) => channels[id]);
     return publicChannels;
 });
-export const getPublicChannelIds: (e: GlobalState, d: Channel, c: boolean, b: boolean, a: SortingType) => Array<string> = createIdsSelector(getPublicChannels, getCurrentUser, getMyChannelMemberships, getLastPostPerChannel, (state, lastUnreadChannel, unreadsAtTop, favoritesAtTop, sorting: SortingType = 'alpha') => sorting, mapAndSortChannelIds);
-export const getSortedPublicChannelIds: (e: GlobalState, d: Channel|null, c: boolean, b: boolean, a: SortingType) => Array<string> = createIdsSelector(getUnreadChannelIds, getFavoritesPreferences, (state, lastUnreadChannel, unreadsAtTop, favoritesAtTop, sorting: SortingType = 'alpha') => getPublicChannelIds(state, lastUnreadChannel, unreadsAtTop, favoritesAtTop, sorting), (state, lastUnreadChannel, unreadsAtTop = true) => unreadsAtTop, (state, lastUnreadChannel, unreadsAtTop, favoritesAtTop = true) => favoritesAtTop, filterChannels); // Private Channels
+
+export const getPublicChannelIds: (e: GlobalState, d: Channel, c: boolean, b: boolean, a: SortingType) => Array<string> = createIdsSelector(getPublicChannels, getCurrentUser, getMyChannelMemberships, getLastPostPerChannel, (state: GlobalState, lastUnreadChannel: Channel, unreadsAtTop: boolean, favoritesAtTop: boolean, sorting: SortingType = 'alpha') => sorting, mapAndSortChannelIds);
+
+export const getSortedPublicChannelIds: (e: GlobalState, d: Channel | null, c: boolean, b: boolean, a: SortingType) => Array<string> = createIdsSelector(getUnreadChannelIds, getFavoritesPreferences, (state: GlobalState, lastUnreadChannel: Channel, unreadsAtTop: boolean, favoritesAtTop: boolean, sorting: SortingType = 'alpha') => getPublicChannelIds(state, lastUnreadChannel, unreadsAtTop, favoritesAtTop, sorting), (state, lastUnreadChannel, unreadsAtTop = true) => unreadsAtTop, (state, lastUnreadChannel, unreadsAtTop, favoritesAtTop = true) => favoritesAtTop, filterChannels); // Private Channels
 
 export const getPrivateChannels: (a: GlobalState) => Array<Channel> = createSelector(getCurrentUser, getAllChannels, getMyChannelMemberships, getChannelIdsForCurrentTeam, (currentUser, channels, myMembers, teamChannelIds) => {
     if (!currentUser) {
@@ -585,10 +604,12 @@ export const getPrivateChannels: (a: GlobalState) => Array<Channel> = createSele
     }).map((id) => channels[id]);
     return privateChannels;
 });
-export const getPrivateChannelIds: (e: GlobalState, d: Channel, c: boolean, b: boolean, a: SortingType) => Array<string> = createIdsSelector(getPrivateChannels, getCurrentUser, getMyChannelMemberships, getLastPostPerChannel, (state, lastUnreadChannel, unreadsAtTop, favoritesAtTop, sorting: SortingType = 'alpha') => sorting, mapAndSortChannelIds);
-export const getSortedPrivateChannelIds: (e: GlobalState, d: Channel|null, c: boolean, b: boolean, a: SortingType) => Array<string> = createIdsSelector(getUnreadChannelIds, getFavoritesPreferences, (state, lastUnreadChannel, unreadsAtTop, favoritesAtTop, sorting: SortingType = 'alpha') => getPrivateChannelIds(state, lastUnreadChannel, unreadsAtTop, favoritesAtTop, sorting), (state, lastUnreadChannel, unreadsAtTop = true) => unreadsAtTop, (state, lastUnreadChannel, unreadsAtTop, favoritesAtTop = true) => favoritesAtTop, filterChannels); // Direct Messages
 
-export const getDirectChannels: (a: GlobalState) => Array<Channel> = createSelector(getCurrentUser, getUsers, getUserIdsInChannels, getAllChannels, getVisibleTeammate, getVisibleGroupIds, getTeammateNameDisplaySetting, getConfig, getMyPreferences, getLastPostPerChannel, getCurrentChannelId, (currentUser: UserProfile, profiles: IDMappedObjects<UserProfile>, userIdsInChannels: any, channels: IDMappedObjects<Channel>, teammates: Array<string>, groupIds: Array<string>, settings: any, config: any, preferences: {
+export const getPrivateChannelIds: (e: GlobalState, d: Channel, c: boolean, b: boolean, a: SortingType) => Array<string> = createIdsSelector(getPrivateChannels, getCurrentUser, getMyChannelMemberships, getLastPostPerChannel, (state: GlobalState, lastUnreadChannel: Channel, unreadsAtTop: boolean, favoritesAtTop: boolean, sorting: SortingType = 'alpha') => sorting, mapAndSortChannelIds);
+
+export const getSortedPrivateChannelIds: (e: GlobalState, d: Channel | null, c: boolean, b: boolean, a: SortingType) => Array<string> = createIdsSelector(getUnreadChannelIds, getFavoritesPreferences, (state: GlobalState, lastUnreadChannel: Channel, unreadsAtTop: boolean, favoritesAtTop: boolean, sorting: SortingType = 'alpha') => getPrivateChannelIds(state, lastUnreadChannel, unreadsAtTop, favoritesAtTop, sorting), (state, lastUnreadChannel, unreadsAtTop = true) => unreadsAtTop, (state, lastUnreadChannel, unreadsAtTop, favoritesAtTop = true) => favoritesAtTop, filterChannels); // Direct Messages
+
+export const getDirectChannels: (a: GlobalState) => Array<Channel> = createSelector(getCurrentUser, getUsers, getUserIdsInChannels, getAllChannels, getVisibleTeammate, getVisibleGroupIds, getTeammateNameDisplaySetting, getConfig, getMyPreferences, getLastPostPerChannel, getCurrentChannelId, (currentUser: UserProfile, profiles: IDMappedObjects<UserProfile>, userIdsInChannels: any, channels: IDMappedObjects<Channel>, teammates: Array<string>, groupIds: Array<string>, settings, config, preferences: {
     [x: string]: PreferenceType;
 }, lastPosts: RelationOneToOne<Channel, Post>, currentChannelId: string): Array<Channel> => {
     if (!currentUser) {
@@ -623,7 +644,7 @@ export const getDirectChannels: (a: GlobalState) => Array<Channel> = createSelec
         return false;
     }).concat(directChannelsIds).map((id) => {
         const channel = channels[id];
-        return completeDirectChannelDisplayName(currentUser.id, profiles, userIdsInChannels[id], settings, channel);
+        return completeDirectChannelDisplayName(currentUser.id, profiles, userIdsInChannels[id], settings!, channel);
     });
     return directChannels;
 }); // getDirectAndGroupChannels returns all direct and group channels, even if they have been manually
@@ -639,10 +660,13 @@ export const getDirectAndGroupChannels: (a: GlobalState) => Array<Channel> = cre
         return [];
     }
 
-    return Object.keys(channels).map((key) => channels[key]).filter((channel: Channel): boolean => Boolean(channel)).filter((channel: Channel): boolean => channel.type === General.DM_CHANNEL || channel.type === General.GM_CHANNEL).map((channel: Channel): Channel => completeDirectChannelDisplayName(currentUser.id, profiles, userIdsInChannels[channel.id], settings, channel));
+    return Object.keys(channels).map((key) => channels[key]).filter((channel: Channel): boolean => Boolean(channel)).filter((channel: Channel): boolean => channel.type === General.DM_CHANNEL || channel.type === General.GM_CHANNEL).map((channel: Channel): Channel => completeDirectChannelDisplayName(currentUser.id, profiles, userIdsInChannels[channel.id], settings!, channel));
 });
-export const getDirectChannelIds: (e: GlobalState, d: Channel, c: boolean, b: boolean, a: SortingType) => Array<string> = createIdsSelector(getDirectChannels, getCurrentUser, getMyChannelMemberships, getLastPostPerChannel, (state, lastUnreadChannel, unreadsAtTop, favoritesAtTop, sorting: SortingType = 'alpha') => sorting, mapAndSortChannelIds);
-export const getSortedDirectChannelIds: (e: GlobalState, d: Channel|null, c: boolean, b: boolean, a: SortingType) => Array<string> = createIdsSelector(getUnreadChannelIds, getFavoritesPreferences, (state, lastUnreadChannel, unreadsAtTop, favoritesAtTop, sorting: SortingType = 'alpha') => getDirectChannelIds(state, lastUnreadChannel, unreadsAtTop, favoritesAtTop, sorting), (state, lastUnreadChannel, unreadsAtTop = true) => unreadsAtTop, (state, lastUnreadChannel, unreadsAtTop, favoritesAtTop = true) => favoritesAtTop, filterChannels);
+
+export const getDirectChannelIds: (e: GlobalState, d: Channel, c: boolean, b: boolean, a: SortingType) => Array<string> = createIdsSelector(getDirectChannels, getCurrentUser, getMyChannelMemberships, getLastPostPerChannel, (state: GlobalState, lastUnreadChannel: Channel, unreadsAtTop: boolean, favoritesAtTop: boolean, sorting: SortingType = 'alpha') => sorting, mapAndSortChannelIds);
+
+export const getSortedDirectChannelIds: (e: GlobalState, d: Channel | null, c: boolean, b: boolean, a: SortingType) => Array<string> = createIdsSelector(getUnreadChannelIds, getFavoritesPreferences, (state: GlobalState, lastUnreadChannel: Channel, unreadsAtTop: boolean, favoritesAtTop: boolean, sorting: SortingType = 'alpha') => getDirectChannelIds(state, lastUnreadChannel, unreadsAtTop, favoritesAtTop, sorting), (state, lastUnreadChannel, unreadsAtTop = true) => unreadsAtTop, (state, lastUnreadChannel, unreadsAtTop, favoritesAtTop = true) => favoritesAtTop, filterChannels);
+
 export function getGroupOrDirectChannelVisibility(state: GlobalState, channelId: string): boolean {
     return isGroupOrDirectChannelVisible(getChannel(state, channelId), getMyChannelMemberships(state), getConfig(state), getMyPreferences(state), getCurrentUser(state).id, getUsers(state), getLastPostPerChannel(state));
 }
@@ -695,11 +719,12 @@ const getAllActiveChannels = createSelector(getPublicChannels, getPrivateChannel
     const allChannels = [...publicChannels, ...privateChannels, ...directChannels];
     return allChannels;
 });
-export const getAllChannelIds: (e: GlobalState, d: Channel, c: boolean, b: boolean, a: SortingType) => Array<string> = createIdsSelector(getAllActiveChannels, getCurrentUser, getMyChannelMemberships, getLastPostPerChannel, (state, lastUnreadChannel, unreadsAtTop, favoritesAtTop, sorting: SortingType = 'alpha') => sorting, mapAndSortChannelIds);
-export const getAllSortedChannelIds: (e: GlobalState, d: Channel| null, c: boolean, b: boolean, a: SortingType) => Array<string> = createIdsSelector(getUnreadChannelIds, getFavoritesPreferences, (state, lastUnreadChannel, unreadsAtTop, favoritesAtTop, sorting: SortingType = 'alpha') => getAllChannelIds(state, lastUnreadChannel, unreadsAtTop, favoritesAtTop, sorting), (state, lastUnreadChannel, unreadsAtTop = true) => unreadsAtTop, (state, lastUnreadChannel, unreadsAtTop, favoritesAtTop = true) => favoritesAtTop, filterChannels);
-let lastChannels;
+export const getAllChannelIds: (e: GlobalState, d: Channel, c: boolean, b: boolean, a: SortingType) => Array<string> = createIdsSelector(getAllActiveChannels, getCurrentUser, getMyChannelMemberships, getLastPostPerChannel, (state: GlobalState, lastUnreadChannel: Channel, unreadsAtTop: boolean, favoritesAtTop: boolean, sorting: SortingType = 'alpha') => sorting, mapAndSortChannelIds);
 
-const hasChannelsChanged = (channels) => {
+export const getAllSortedChannelIds: (e: GlobalState, d: Channel | null, c: boolean, b: boolean, a: SortingType) => Array<string> = createIdsSelector(getUnreadChannelIds, getFavoritesPreferences, (state: GlobalState, lastUnreadChannel: Channel, unreadsAtTop: boolean, favoritesAtTop: boolean, sorting: SortingType = 'alpha') => getAllChannelIds(state, lastUnreadChannel, unreadsAtTop, favoritesAtTop, sorting), (state, lastUnreadChannel, unreadsAtTop = true) => unreadsAtTop, (state, lastUnreadChannel, unreadsAtTop, favoritesAtTop = true) => favoritesAtTop, filterChannels);
+let lastChannels: {type: string;name: string;items: string[]}[];
+
+const hasChannelsChanged = (channels: {type: string;name: string;items: string[]}[]) => {
     if (!lastChannels || lastChannels.length !== channels.length) {
         return true;
     }
@@ -714,7 +739,7 @@ const hasChannelsChanged = (channels) => {
 };
 
 export const getOrderedChannelIds = (state: GlobalState, lastUnreadChannel: Channel|null, grouping: 'by_type' | 'none', sorting: SortingType, unreadsAtTop: boolean, favoritesAtTop: boolean) => {
-    const channels: {type;name;items}[] = [];
+    const channels: {type: string;name: string;items: string[]}[] = [];
 
     if (grouping === 'by_type') {
         channels.push({
@@ -770,21 +795,27 @@ export const getOrderedChannelIds = (state: GlobalState, lastUnreadChannel: Chan
     }
 
     return lastChannels;
-}; // Added for backwards compatibility
+};
+
+// Added for backwards compatibility
 // Can be removed once webapp includes new sidebar preferences
 
 export const getSortedPublicChannelWithUnreadsIds: (e: GlobalState, d: Channel, c: boolean, b: boolean, a: SortingType) => Array<string> = createIdsSelector(getUnreadChannelIds, getFavoritesPreferences, getPublicChannelIds, (state, lastUnreadChannel, unreadsAtTop, favoritesAtTop = true) => favoritesAtTop, (unreadChannelIds, favoritePreferences, publicChannelIds, favoritesAtTop) => {
     return filterChannels(unreadChannelIds, favoritePreferences, publicChannelIds, false, favoritesAtTop);
 });
+
 export const getSortedPrivateChannelWithUnreadsIds: (e: GlobalState, d: Channel, c: boolean, b: boolean, a: SortingType) => Array<string> = createIdsSelector(getUnreadChannelIds, getFavoritesPreferences, getPrivateChannelIds, (state, lastUnreadChannel, unreadsAtTop, favoritesAtTop = true) => favoritesAtTop, (unreadChannelIds, favoritePreferences, privateChannelId, favoritesAtTop) => {
     return filterChannels(unreadChannelIds, favoritePreferences, privateChannelId, false, favoritesAtTop);
 });
+
 export const getSortedFavoriteChannelWithUnreadsIds: (e: GlobalState, d: Channel, c: boolean, b: boolean, a: SortingType) => Array<string> = createIdsSelector(getUnreadChannelIds, getFavoriteChannelIds, (unreadChannelIds, favoriteChannelIds) => favoriteChannelIds);
+
 export const getSortedDirectChannelWithUnreadsIds: (e: GlobalState, d: Channel, c: boolean, b: boolean, a: SortingType) => Array<string> = createIdsSelector(getUnreadChannelIds, getFavoritesPreferences, getDirectChannelIds, (state, lastUnreadChannel, unreadsAtTop, favoritesAtTop = true) => favoritesAtTop, (unreadChannelIds, favoritePreferences, directChannelIds, favoritesAtTop) => {
     return filterChannels(unreadChannelIds, favoritePreferences, directChannelIds, false, favoritesAtTop);
 });
+
 export const getDefaultChannelForTeams: (a: GlobalState) => RelationOneToOne<Team, Channel> = createSelector(getAllChannels, (channels: IDMappedObjects<Channel>): RelationOneToOne<Team, Channel> => {
-    const result = {};
+    const result: RelationOneToOne<Team, Channel> = {};
 
     for (const channel of Object.keys(channels).map((key) => channels[key])) {
         if (channel && channel.name === General.DEFAULT_CHANNEL) {
@@ -794,13 +825,13 @@ export const getDefaultChannelForTeams: (a: GlobalState) => RelationOneToOne<Tea
 
     return result;
 });
+
 export const getMyFirstChannelForTeams: (a: GlobalState) => RelationOneToOne<Team, Channel> = createSelector(getAllChannels, getMyChannelMemberships, getMyTeams, getCurrentUser, (allChannels: IDMappedObjects<Channel>, myChannelMemberships: RelationOneToOne<Channel, ChannelMembership>, myTeams: Array<Team>, currentUser: UserProfile): RelationOneToOne<Team, Channel> => {
     const locale = currentUser.locale || General.DEFAULT_LOCALE;
-    const result = {};
+    const result: RelationOneToOne<Team, Channel> = {};
 
     for (const team of myTeams) {
     // Get a sorted array of all channels in the team that the current user is a member of
-    // $FlowFixMe
         const teamChannels = Object.values(allChannels).filter((channel: Channel) => channel && channel.team_id === team.id && Boolean(myChannelMemberships[channel.id])).sort(sortChannelsByDisplayName.bind(null, locale));
 
         if (teamChannels.length === 0) {
diff --git a/src/selectors/entities/files.ts b/src/selectors/entities/files.ts
index 2bba7cee1..07f6647fd 100644
--- a/src/selectors/entities/files.ts
+++ b/src/selectors/entities/files.ts
@@ -8,6 +8,7 @@ import {getCurrentUserLocale} from 'selectors/entities/i18n';
 import {sortFileInfos} from 'utils/file_utils';
 
 import * as types from 'types';
+import {GlobalState} from 'types/store';
 
 function getAllFiles(state: types.store.GlobalState) {
     return state.entities.files.files;
@@ -21,7 +22,7 @@ function getFilesIdsForPost(state: types.store.GlobalState, postId: string) {
     return [];
 }
 
-export function getFilePublicLink(state) {
+export function getFilePublicLink(state: GlobalState) {
     return state.entities.files.filePublicLink;
 }
 
diff --git a/src/selectors/entities/general.ts b/src/selectors/entities/general.ts
index 4692b5ec3..0217c84cb 100644
--- a/src/selectors/entities/general.ts
+++ b/src/selectors/entities/general.ts
@@ -4,7 +4,9 @@ import {createSelector} from 'reselect';
 import {isMinimumServerVersion} from 'utils/helpers';
 import {General} from '../../constants';
 import {GlobalState} from 'types/store';
-export function getConfig(state: GlobalState): any {
+import {Config} from 'types/config';
+
+export function getConfig(state: GlobalState): Partial<Config> {
     return state.entities.general.config;
 }
 
@@ -39,7 +41,7 @@ export function hasNewPermissions(state: GlobalState): boolean {
 export const canUploadFilesOnMobile: (a: GlobalState) => boolean = createSelector(
     getConfig,
     getLicense,
-    (config: any, license: any): boolean => {
+    (config: Config, license: any): boolean => {
         // Defaults to true if either setting doesn't exist
         return config.EnableFileAttachments !== 'false' &&
            (license.IsLicensed === 'false' || license.Compliance === 'false' || config.EnableMobileFileUpload !== 'false');
@@ -49,7 +51,7 @@ export const canUploadFilesOnMobile: (a: GlobalState) => boolean = createSelecto
 export const canDownloadFilesOnMobile: (a: GlobalState) => boolean = createSelector(
     getConfig,
     getLicense,
-    (config: any, license: any): boolean => {
+    (config: Config, license: any): boolean => {
         // Defaults to true if the setting doesn't exist
         return license.IsLicensed === 'false' || license.Compliance === 'false' || config.EnableMobileFileDownload !== 'false';
     }
@@ -57,7 +59,7 @@ export const canDownloadFilesOnMobile: (a: GlobalState) => boolean = createSelec
 
 export const getAutolinkedUrlSchemes: (a: GlobalState) => string[] = createSelector(
     getConfig,
-    (config: any): string[] => {
+    (config: Config): string[] => {
         if (!config.CustomUrlSchemes) {
             return General.DEFAULT_AUTOLINKED_URL_SCHEMES;
         }
diff --git a/src/selectors/entities/groups.ts b/src/selectors/entities/groups.ts
index d93647e03..13078ee84 100644
--- a/src/selectors/entities/groups.ts
+++ b/src/selectors/entities/groups.ts
@@ -2,21 +2,21 @@
 // See LICENSE.txt for license information.
 import * as reselect from 'reselect';
 import {GlobalState} from 'types/store';
-const emptyList = [];
+const emptyList: any[] = [];
 const emptySyncables = {
     teams: [],
     channels: [],
 };
 
-export function getAllGroups(state) {
+export function getAllGroups(state: GlobalState) {
     return state.entities.groups.groups;
 }
 
-export function getGroup(state, id) {
+export function getGroup(state: GlobalState, id: string) {
     return getAllGroups(state)[id];
 }
 
-export function getGroupMemberCount(state, id) {
+export function getGroupMemberCount(state: GlobalState, id: string) {
     const memberData = state.entities.groups.members;
     const groupMemberData = memberData[id];
     if (!groupMemberData) {
@@ -25,19 +25,19 @@ export function getGroupMemberCount(state, id) {
     return memberData[id].totalMemberCount;
 }
 
-function getGroupSyncables(state, id) {
+function getGroupSyncables(state: GlobalState, id: string) {
     return state.entities.groups.syncables[id] || emptySyncables;
 }
 
-export function getGroupTeams(state, id) {
+export function getGroupTeams(state: GlobalState, id: string) {
     return getGroupSyncables(state, id).teams;
 }
 
-export function getGroupChannels(state, id) {
+export function getGroupChannels(state: GlobalState, id: string) {
     return getGroupSyncables(state, id).channels;
 }
 
-export function getGroupMembers(state, id) {
+export function getGroupMembers(state: GlobalState, id: string) {
     const groupMemberData = state.entities.groups.members[id];
     if (!groupMemberData) {
         return emptyList;
@@ -45,9 +45,9 @@ export function getGroupMembers(state, id) {
     return groupMemberData.members;
 }
 
-const teamGroupIDs = (state: GlobalState, teamID) => (state.entities.teams.groupsAssociatedToTeam[teamID] == null ? undefined : state.entities.teams.groupsAssociatedToTeam[teamID].ids == null ? undefined : state.entities.teams.groupsAssociatedToTeam[teamID].ids) || [];
+const teamGroupIDs = (state: GlobalState, teamID: string) => (state.entities.teams.groupsAssociatedToTeam[teamID] == null ? undefined : state.entities.teams.groupsAssociatedToTeam[teamID].ids == null ? undefined : state.entities.teams.groupsAssociatedToTeam[teamID].ids) || [];
 
-const channelGroupIDs = (state: GlobalState, channelID) => (state.entities.channels.groupsAssociatedToChannel[channelID] == null ? undefined : state.entities.channels.groupsAssociatedToChannel[channelID].ids == null ? undefined : state.entities.channels.groupsAssociatedToChannel[channelID].ids) || [];
+const channelGroupIDs = (state: GlobalState, channelID: string) => (state.entities.channels.groupsAssociatedToChannel[channelID] == null ? undefined : state.entities.channels.groupsAssociatedToChannel[channelID].ids == null ? undefined : state.entities.channels.groupsAssociatedToChannel[channelID].ids) || [];
 
 const getTeamGroupIDSet = reselect.createSelector(
     teamGroupIDs,
@@ -61,7 +61,7 @@ const getChannelGroupIDSet = reselect.createSelector(
 
 export const getGroupsNotAssociatedToTeam = reselect.createSelector(
     getAllGroups,
-    (state, teamID) => getTeamGroupIDSet(state, teamID),
+    (state: GlobalState, teamID: string) => getTeamGroupIDSet(state, teamID),
     (allGroups, teamGroupIDSet) => {
         return Object.entries(allGroups).filter(([groupID]) => !teamGroupIDSet.has(groupID)).map((entry) => entry[1]);
     }
@@ -69,7 +69,7 @@ export const getGroupsNotAssociatedToTeam = reselect.createSelector(
 
 export const getGroupsAssociatedToTeam = reselect.createSelector(
     getAllGroups,
-    (state, teamID) => getTeamGroupIDSet(state, teamID),
+    (state: GlobalState, teamID: string) => getTeamGroupIDSet(state, teamID),
     (allGroups, teamGroupIDSet) => {
         return Object.entries(allGroups).filter(([groupID]) => teamGroupIDSet.has(groupID)).map((entry) => entry[1]);
     }
@@ -77,7 +77,7 @@ export const getGroupsAssociatedToTeam = reselect.createSelector(
 
 export const getGroupsNotAssociatedToChannel = reselect.createSelector(
     getAllGroups,
-    (state, channelID) => getChannelGroupIDSet(state, channelID),
+    (state: GlobalState, channelID: string) => getChannelGroupIDSet(state, channelID),
     (allGroups, channelGroupIDSet) => {
         return Object.entries(allGroups).filter(([groupID]) => !channelGroupIDSet.has(groupID)).map((entry) => entry[1]);
     }
@@ -85,7 +85,7 @@ export const getGroupsNotAssociatedToChannel = reselect.createSelector(
 
 export const getGroupsAssociatedToChannel = reselect.createSelector(
     getAllGroups,
-    (state, channelID) => getChannelGroupIDSet(state, channelID),
+    (state: GlobalState, channelID: string) => getChannelGroupIDSet(state, channelID),
     (allGroups, channelGroupIDSet) => {
         return Object.entries(allGroups).filter(([groupID]) => channelGroupIDSet.has(groupID)).map((entry) => entry[1]);
     }
diff --git a/src/selectors/entities/integrations.test.js b/src/selectors/entities/integrations.test.js
index 348913d25..6a0091256 100644
--- a/src/selectors/entities/integrations.test.js
+++ b/src/selectors/entities/integrations.test.js
@@ -5,7 +5,7 @@ import assert from 'assert';
 import TestHelper from 'test/test_helper';
 import deepFreezeAndThrowOnMutation from 'utils/deep_freeze';
 
-import {getAllCommands, getAutocompleteCommandsList, getOutgoingHooksInCurrentTeam} from 'selectors/entities/integrations';
+import {getAllCommands, getAutocompleteCommandsList, getOutgoingHooksInCurrentTeam} from './integrations';
 
 describe('Selectors.Integrations', () => {
     TestHelper.initBasic();
diff --git a/src/selectors/entities/integrations.ts b/src/selectors/entities/integrations.ts
index 8a0c872b7..8d5176e54 100644
--- a/src/selectors/entities/integrations.ts
+++ b/src/selectors/entities/integrations.ts
@@ -33,7 +33,7 @@ export const getOutgoingHooksInCurrentTeam = reselect.createSelector(
     getCurrentTeamId,
     getOutgoingHooks,
     (teamId, hooks) => {
-        return Object.values(hooks).filter((o) => o.teamId === teamId);
+        return Object.values(hooks).filter((o) => o.team_id === teamId);
     }
 );
 
diff --git a/src/selectors/entities/plugins.ts b/src/selectors/entities/plugins.ts
index bedd4c93c..4035c505b 100644
--- a/src/selectors/entities/plugins.ts
+++ b/src/selectors/entities/plugins.ts
@@ -2,14 +2,15 @@
 // See LICENSE.txt for license information.
 
 import * as reselect from 'reselect';
+import {GlobalState} from 'types/store';
 
-export function getMarketplacePlugins(state) {
+export function getMarketplacePlugins(state: GlobalState) {
     return state.entities.plugins.marketplacePlugins;
 }
 
 export const getMarketplaceInstalledPlugins = reselect.createSelector(
     getMarketplacePlugins,
     (plugins) => {
-        return Object.values(plugins).filter((p: any) => p.installed_version !== '');
+        return Object.values(plugins).filter((p) => p.installed_version !== '');
     }
 );
diff --git a/src/selectors/entities/posts.ts b/src/selectors/entities/posts.ts
index d75e24b58..9f16489ef 100644
--- a/src/selectors/entities/posts.ts
+++ b/src/selectors/entities/posts.ts
@@ -8,11 +8,11 @@ import {Posts, Preferences} from '../../constants';
 import {isPostEphemeral, isSystemMessage, shouldFilterJoinLeavePost, comparePosts, isPostPendingOrFailed, isPostCommentMention} from 'utils/post_utils';
 import {getPreferenceKey} from 'utils/preference_utils';
 import {GlobalState} from 'types/store';
-import {Post, PostWithFormatData} from 'types/posts';
+import {Post, PostWithFormatData, MessageHistory, PostOrderBlock} from 'types/posts';
 import {Reaction} from 'types/reactions';
 import {UserProfile} from 'types/users';
 import {Channel} from 'types/channels';
-import {$ID, IDMappedObjects, RelationOneToOne, RelationOneToMany} from 'types/utilities';
+import {$ID, IDMappedObjects, RelationOneToOne, RelationOneToMany, Dictionary} from 'types/utilities';
 export function getAllPosts(state: GlobalState) {
     return state.entities.posts.posts;
 }
@@ -34,7 +34,7 @@ export function getReactionsForPosts(state: GlobalState): RelationOneToOne<Post,
 export function makeGetReactionsForPost(): (b: GlobalState, a: $ID<Post>) => {
   [x: string]: Reaction;
 } | undefined | null {
-    return createSelector(getReactionsForPosts, (state: GlobalState, postId) => postId, (reactions, postId) => {
+    return createSelector(getReactionsForPosts, (state: GlobalState, postId: string) => postId, (reactions, postId) => {
         if (reactions[postId]) {
             return reactions[postId];
         }
@@ -68,7 +68,7 @@ export const getPostsInCurrentChannel: (a: GlobalState) => Array<PostWithFormatD
 export function makeGetPostIdsForThread(): (b: GlobalState, a: $ID<Post>) => Array<$ID<Post>> {
     return createIdsSelector(
         getAllPosts,
-        (state: GlobalState, rootId) => state.entities.posts.postsInThread[rootId] || [],
+        (state: GlobalState, rootId: string) => state.entities.posts.postsInThread[rootId] || [],
         (state: GlobalState, rootId) => state.entities.posts.posts[rootId],
         (posts, postsForThread, rootPost) => {
             const thread: Post[] = [];
@@ -91,9 +91,9 @@ export function makeGetPostIdsForThread(): (b: GlobalState, a: $ID<Post>) => Arr
     );
 }
 
-export function makeGetPostsChunkAroundPost(): (c: GlobalState, b: $ID<Post>, a: $ID<Channel>) => any {
+export function makeGetPostsChunkAroundPost(): (c: GlobalState, b: $ID<Post>, a: $ID<Channel>) => PostOrderBlock| null | undefined {
     return createIdsSelector(
-        (state: GlobalState, postId, channelId) => state.entities.posts.postsInChannel[channelId],
+        (state: GlobalState, postId: string, channelId: string) => state.entities.posts.postsInChannel[channelId],
         (state: GlobalState, postId) => postId,
         (postsForChannel, postId) => {
             if (!postsForChannel) {
@@ -123,7 +123,7 @@ export function makeGetPostIdsAroundPost(): (d: GlobalState, c: $ID<Post>, b: $I
 }) => Array<$ID<Post>> | undefined | null {
     const getPostsChunkAroundPost = makeGetPostsChunkAroundPost();
     return createIdsSelector(
-        (state: GlobalState, postId, channelId) => getPostsChunkAroundPost(state, postId, channelId),
+        (state: GlobalState, postId: string, channelId: string) => getPostsChunkAroundPost(state, postId, channelId),
         (state: GlobalState, postId) => postId,
         (state: GlobalState, postId, channelId, options) => options && options.postsBeforeCount,
         (state: GlobalState, postId, channelId, options) => options && options.postsAfterCount,
@@ -148,7 +148,7 @@ function formatPostInChannel(post: Post, previousPost: Post | undefined | null,
     let isFirstReply = false;
     let isLastReply = false;
     let highlight = false;
-    let commentedOnPost;
+    let commentedOnPost: Post| undefined;
 
     if (post.id === focusedPostId) {
         highlight = true;
@@ -276,7 +276,7 @@ export function makeGetPostsAroundPost(): (c: GlobalState, b: $ID<Post>, a: $ID<
     };
 
     return createSelector(
-        (state: GlobalState, focusedPostId, channelId) => getPostIdsAroundPost(state, focusedPostId, channelId, options),
+        (state: GlobalState, focusedPostId: string, channelId: string) => getPostIdsAroundPost(state, focusedPostId, channelId, options),
         getAllPosts,
         getPostsInThread,
         (state: GlobalState, focusedPostId) => focusedPostId,
@@ -318,7 +318,7 @@ export function makeGetPostsForThread(): (b: GlobalState, a: {
 }) => Array<Post> {
     return createSelector(getAllPosts, (state: GlobalState, {
         rootId,
-    }) => state.entities.posts.postsInThread[rootId] || [], (state: GlobalState, {
+    }: {rootId: string}) => state.entities.posts.postsInThread[rootId] || [], (state: GlobalState, {
         rootId,
     }) => state.entities.posts.posts[rootId], (posts, postsForThread, rootPost) => {
         const thread: Post[] = [];
@@ -344,7 +344,7 @@ export function makeGetCommentCountForPost(): (b: GlobalState, a: {
 }) => number {
     return createSelector(
         getAllPosts,
-        (state, {post}) => state.entities.posts.postsInThread[post ? post.id : ''] || [],
+        (state: GlobalState, {post}: {post: Post}) => state.entities.posts.postsInThread[post ? post.id : ''] || [],
         (state, props) => props,
         (posts, postsForThread, {post: currentPost}) => {
             if (!currentPost) {
@@ -385,10 +385,10 @@ export function getSearchMatches(state: GlobalState): {
     return state.entities.search.matches;
 }
 
-export function makeGetMessageInHistoryItem(type: string): (a: GlobalState) => string {
+export function makeGetMessageInHistoryItem(type: 'post'|'comment'): (a: GlobalState) => string {
     return createSelector(
         (state: GlobalState) => state.entities.posts.messagesHistory,
-        (messagesHistory) => {
+        (messagesHistory: MessageHistory) => {
             const idx = messagesHistory.index[type];
             const messages = messagesHistory.messages;
             if (idx >= 0 && messages && messages.length > idx) {
@@ -402,7 +402,7 @@ export function makeGetMessageInHistoryItem(type: string): (a: GlobalState) => s
 export function makeGetPostsForIds(): (b: GlobalState, a: Array<$ID<Post>>) => Array<Post> {
     return createIdsSelector(
         getAllPosts,
-        (state: GlobalState, postIds) => postIds,
+        (state: GlobalState, postIds: Array<$ID<Post>>) => postIds,
         (allPosts, postIds) => {
             if (!postIds) {
                 return [];
@@ -417,10 +417,10 @@ export const getLastPostPerChannel: (a: GlobalState) => RelationOneToOne<Channel
     getAllPosts,
     (state: GlobalState) => state.entities.posts.postsInChannel,
     (allPosts, postsInChannel) => {
-        const ret = {};
+        const ret: Dictionary<Post> = {};
 
         for (const [channelId, postsForChannel] of Object.entries(postsInChannel)) {
-            const recentBlock = (postsForChannel as any).find((block) => block.recent);
+            const recentBlock = (postsForChannel).find((block) => block.recent);
             if (!recentBlock) {
                 continue;
             }
@@ -434,7 +434,7 @@ export const getLastPostPerChannel: (a: GlobalState) => RelationOneToOne<Channel
         return ret;
     }
 );
-export const getMostRecentPostIdInChannel: (b: GlobalState, a: $ID<Channel>) => $ID<Post> | undefined | null = createSelector(getAllPosts, (state: GlobalState, channelId) => getPostIdsInChannel(state, channelId), getMyPreferences, (posts, postIdsInChannel, preferences) => {
+export const getMostRecentPostIdInChannel: (b: GlobalState, a: $ID<Channel>) => $ID<Post> | undefined | null = createSelector(getAllPosts, (state: GlobalState, channelId: string) => getPostIdsInChannel(state, channelId), getMyPreferences, (posts, postIdsInChannel, preferences) => {
     if (!postIdsInChannel) {
         return '';
     }
@@ -474,7 +474,8 @@ export const getLatestReplyablePostId: (a: GlobalState) => $ID<Post> = createSel
         return latestReplyablePost.id;
     }
 );
-export const getCurrentUsersLatestPost: (b: GlobalState, a: $ID<Post>) => PostWithFormatData | undefined | null = createSelector(getPostsInCurrentChannel, getCurrentUser, (_, rootId) => rootId, (posts, currentUser, rootId) => {
+
+export const getCurrentUsersLatestPost: (b: GlobalState, a: $ID<Post>) => PostWithFormatData | undefined | null = createSelector(getPostsInCurrentChannel, getCurrentUser, (_: any, rootId: string) => rootId, (posts, currentUser, rootId) => {
     if (!posts) {
         return null;
     }
@@ -493,7 +494,8 @@ export const getCurrentUsersLatestPost: (b: GlobalState, a: $ID<Post>) => PostWi
     });
     return lastPost;
 });
-export function getRecentPostsChunkInChannel(state: GlobalState, channelId: $ID<Channel>): any {
+
+export function getRecentPostsChunkInChannel(state: GlobalState, channelId: $ID<Channel>): PostOrderBlock|null|undefined {
     const postsForChannel = state.entities.posts.postsInChannel[channelId];
 
     if (!postsForChannel) {
@@ -503,7 +505,7 @@ export function getRecentPostsChunkInChannel(state: GlobalState, channelId: $ID<
     return postsForChannel.find((block) => block.recent);
 }
 
-export function getOldestPostsChunkInChannel(state: GlobalState, channelId: $ID<Channel>): any {
+export function getOldestPostsChunkInChannel(state: GlobalState, channelId: $ID<Channel>): PostOrderBlock|null|undefined {
     const postsForChannel = state.entities.posts.postsInChannel[channelId];
 
     if (!postsForChannel) {
diff --git a/src/selectors/entities/preferences.ts b/src/selectors/entities/preferences.ts
index e8746ec63..085bffeb8 100644
--- a/src/selectors/entities/preferences.ts
+++ b/src/selectors/entities/preferences.ts
@@ -8,11 +8,12 @@ import {createShallowSelector} from 'utils/helpers';
 import {getPreferenceKey} from 'utils/preference_utils';
 import {GlobalState} from 'types/store';
 import {PreferencesType, PreferenceType} from 'types/preferences';
-export function getMyPreferences(state) {
+
+export function getMyPreferences(state: GlobalState) {
     return state.entities.preferences.myPreferences;
 }
 
-export function get(state: GlobalState, category, name, defaultValue: any = '') {
+export function get(state: GlobalState, category: string, name: string, defaultValue: any = '') {
     const key = getPreferenceKey(category, name);
     const prefs = getMyPreferences(state);
 
@@ -23,12 +24,12 @@ export function get(state: GlobalState, category, name, defaultValue: any = '')
     return prefs[key].value;
 }
 
-export function getBool(state, category, name, defaultValue = false) {
+export function getBool(state: GlobalState, category: string, name: string, defaultValue = false) {
     const value = get(state, category, name, String(defaultValue));
     return value !== 'false';
 }
 
-export function getInt(state, category, name, defaultValue = 0) {
+export function getInt(state: GlobalState, category: string, name: string, defaultValue = 0) {
     const value = get(state, category, name, defaultValue);
     return parseInt(value, 10);
 }
@@ -36,7 +37,7 @@ export function getInt(state, category, name, defaultValue = 0) {
 export function makeGetCategory() {
     return reselect.createSelector(
         getMyPreferences,
-        (state, category) => category,
+        (state: GlobalState, category: string) => category,
         (preferences, category) => {
             const prefix = category + '--';
             const prefsInCategory: PreferenceType[] = [];
@@ -54,19 +55,19 @@ export function makeGetCategory() {
 
 const getDirectShowCategory = makeGetCategory();
 
-export function getDirectShowPreferences(state) {
+export function getDirectShowPreferences(state: GlobalState) {
     return getDirectShowCategory(state, Preferences.CATEGORY_DIRECT_CHANNEL_SHOW);
 }
 
 const getGroupShowCategory = makeGetCategory();
 
-export function getGroupShowPreferences(state) {
+export function getGroupShowPreferences(state: GlobalState) {
     return getGroupShowCategory(state, Preferences.CATEGORY_GROUP_CHANNEL_SHOW);
 }
 
 const getFavoritesCategory = makeGetCategory();
 
-export function getFavoritesPreferences(state) {
+export function getFavoritesPreferences(state: GlobalState) {
     const favorites = getFavoritesCategory(state, Preferences.CATEGORY_FAVORITE_CHANNEL);
     return favorites.filter((f) => f.value === 'true').map((f) => f.name);
 }
@@ -134,7 +135,7 @@ export const getTheme = createShallowSelector(
     getThemePreference,
     getDefaultTheme,
     (themePreference, defaultTheme) => {
-        let theme;
+        let theme: any;
         if (themePreference) {
             theme = themePreference.value;
         } else {
@@ -150,7 +151,7 @@ export const getTheme = createShallowSelector(
 
         // If this is a system theme, find it in case the user's theme is missing any fields
         if (theme.type && theme.type !== 'custom') {
-            const match = Object.values(Preferences.THEMES).find((v) => v.type === theme.type);
+            const match = Object.values(Preferences.THEMES).find((v: any) => v.type === theme.type) as any;
             if (match) {
                 if (!match.mentionBg) {
                     match.mentionBg = match.mentionBj;
@@ -179,7 +180,7 @@ export const getTheme = createShallowSelector(
 export function makeGetStyleFromTheme() {
     return reselect.createSelector(
         getTheme,
-        (state, getStyleFromTheme) => getStyleFromTheme,
+        (state: GlobalState, getStyleFromTheme: Function) => getStyleFromTheme,
         (theme, getStyleFromTheme) => {
             return getStyleFromTheme(theme);
         }
diff --git a/src/selectors/entities/roles.ts b/src/selectors/entities/roles.ts
index 7a9587267..3e10d70ec 100644
--- a/src/selectors/entities/roles.ts
+++ b/src/selectors/entities/roles.ts
@@ -4,14 +4,19 @@ import * as reselect from 'reselect';
 import {getCurrentUser, getCurrentChannelId} from 'selectors/entities/common';
 import {getTeamMemberships, getCurrentTeamId} from './teams';
 import * as types from 'types';
-import {getMySystemPermissions, getMySystemRoles, getRoles} from 'selectors/entities/roles_helpers';
+import {getMySystemPermissions, getMySystemRoles, getRoles, PermissionsOptions} from 'selectors/entities/roles_helpers';
+import {GlobalState} from 'types/store';
+import {Dictionary} from 'types/utilities';
+import {Role} from 'types/roles';
+import {Channel} from 'types/channels';
+import {Team} from 'types/teams';
 
 export {getMySystemPermissions, getMySystemRoles, getRoles};
 
 export const getMyTeamRoles = reselect.createSelector(
     getTeamMemberships,
     (teamsMemberships) => {
-        const roles = {};
+        const roles: Dictionary<Set<string>> = {};
         if (teamsMemberships) {
             for (const key in teamsMemberships) {
                 if (teamsMemberships.hasOwnProperty(key) && teamsMemberships[key].roles) {
@@ -26,7 +31,7 @@ export const getMyTeamRoles = reselect.createSelector(
 export const getMyChannelRoles = reselect.createSelector(
     (state: types.store.GlobalState) => state.entities.channels.myMembers,
     (channelsMemberships) => {
-        const roles = {};
+        const roles: Dictionary<Set<string>> = {};
         if (channelsMemberships) {
             for (const key in channelsMemberships) {
                 if (channelsMemberships.hasOwnProperty(key) && channelsMemberships[key].roles) {
@@ -54,7 +59,7 @@ export const getMyRoles = reselect.createSelector(
 export const getRolesById = reselect.createSelector(
     getRoles,
     (rolesByName) => {
-        const rolesById = {};
+        const rolesById: Dictionary<Role> = {};
         for (const role of Object.values(rolesByName)) {
             rolesById[role.id] = role;
         }
@@ -112,11 +117,11 @@ export const getMyTeamPermissions = reselect.createSelector(
     getMyTeamRoles,
     getRoles,
     getMySystemPermissions,
-    (state, options) => options.team,
+    (state: GlobalState, options: PermissionsOptions) => options.team,
     (myTeamRoles, roles, systemPermissions, teamId) => {
         const permissions = new Set();
-        if (myTeamRoles[teamId]) {
-            for (const roleName of myTeamRoles[teamId]) {
+        if (myTeamRoles[teamId!]) {
+            for (const roleName of myTeamRoles[teamId!]) {
                 if (roles[roleName]) {
                     for (const permission of roles[roleName].permissions) {
                         permissions.add(permission);
@@ -135,11 +140,11 @@ export const getMyChannelPermissions = reselect.createSelector(
     getMyChannelRoles,
     getRoles,
     getMyTeamPermissions,
-    (state, options) => options.channel,
+    (state, options: PermissionsOptions) => options.channel,
     (myChannelRoles, roles, teamPermissions, channelId) => {
         const permissions = new Set();
-        if (myChannelRoles[channelId]) {
-            for (const roleName of myChannelRoles[channelId]) {
+        if (myChannelRoles[channelId!]) {
+            for (const roleName of myChannelRoles[channelId!]) {
                 if (roles[roleName]) {
                     for (const permission of roles[roleName].permissions) {
                         permissions.add(permission);
@@ -156,7 +161,7 @@ export const getMyChannelPermissions = reselect.createSelector(
 
 export const haveISystemPermission = reselect.createSelector(
     getMySystemPermissions,
-    (state, options) => options.permission,
+    (state: GlobalState, options: PermissionsOptions) => options.permission,
     (permissions, permission) => {
         return permissions.has(permission);
     }
@@ -180,7 +185,7 @@ export const haveIChannelPermission = reselect.createSelector(
 
 export const haveICurrentTeamPermission = reselect.createSelector(
     getMyCurrentTeamPermissions,
-    (state, options) => options.permission,
+    (state: GlobalState, options: PermissionsOptions) => options.permission,
     (permissions, permission) => {
         return permissions.has(permission);
     }
@@ -188,7 +193,7 @@ export const haveICurrentTeamPermission = reselect.createSelector(
 
 export const haveICurrentChannelPermission = reselect.createSelector(
     getMyCurrentChannelPermissions,
-    (state, options) => options.permission,
+    (state: GlobalState, options: PermissionsOptions) => options.permission,
     (permissions, permission) => {
         return permissions.has(permission);
     }
diff --git a/src/selectors/entities/roles_helpers.ts b/src/selectors/entities/roles_helpers.ts
index cc4f2e3b1..6cab7b8b5 100644
--- a/src/selectors/entities/roles_helpers.ts
+++ b/src/selectors/entities/roles_helpers.ts
@@ -5,6 +5,12 @@ import {GlobalState} from 'types/store';
 import {getCurrentUser} from 'selectors/entities/common';
 import * as types from 'types';
 
+export type PermissionsOptions = {
+    channel?: string;
+    team?: string;
+    permission: string;
+};
+
 export function getRoles(state: GlobalState) {
     return state.entities.roles.roles;
 }
@@ -31,6 +37,6 @@ export const getMySystemPermissions = reselect.createSelector(getMySystemRoles,
     return permissions;
 });
 
-export const haveISystemPermission = reselect.createSelector(getMySystemPermissions, (state, options) => options.permission, (permissions, permission) => {
+export const haveISystemPermission = reselect.createSelector(getMySystemPermissions, (state: GlobalState, options: PermissionsOptions) => options.permission, (permissions, permission) => {
     return permissions.has(permission);
 });
diff --git a/src/selectors/entities/schemes.ts b/src/selectors/entities/schemes.ts
index 4c30ac997..818de62a4 100644
--- a/src/selectors/entities/schemes.ts
+++ b/src/selectors/entities/schemes.ts
@@ -9,6 +9,7 @@ import {GlobalState} from 'types/store';
 import {Scheme} from 'types/schemes';
 import {Channel} from 'types/channels';
 import {Team} from 'types/teams';
+
 export function getSchemes(state: GlobalState): {
     [x: string]: Scheme;
 } {
@@ -23,7 +24,7 @@ export function getScheme(state: GlobalState, id: string): Scheme {
 export function makeGetSchemeChannels() {
     return (createSelector(
         getAllChannels,
-        (state, props: {schemeId: string}) => getScheme(state, props.schemeId),
+        (state: GlobalState, props: {schemeId: string}) => getScheme(state, props.schemeId),
         (allChannels, scheme) => {
             if (!scheme) {
                 return [];
@@ -53,7 +54,7 @@ export function makeGetSchemeChannels() {
 export function makeGetSchemeTeams() {
     return (createSelector(
         getTeams,
-        (state, props: {schemeId: string}) => getScheme(state, props.schemeId),
+        (state: GlobalState, props: {schemeId: string}) => getScheme(state, props.schemeId),
         (allTeams, scheme) => {
             if (!scheme) {
                 return [];
diff --git a/src/selectors/entities/timezone.ts b/src/selectors/entities/timezone.ts
index eb7718c0f..189c73e34 100644
--- a/src/selectors/entities/timezone.ts
+++ b/src/selectors/entities/timezone.ts
@@ -1,7 +1,9 @@
 // Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
 // See LICENSE.txt for license information.
 
-export function getUserTimezone(state, id) {
+import {GlobalState} from 'types/store';
+
+export function getUserTimezone(state: GlobalState, id: string) {
     const profile = state.entities.users.profiles[id];
 
     if (profile && profile.timezone) {
@@ -18,7 +20,7 @@ export function getUserTimezone(state, id) {
     };
 }
 
-export function isTimezoneEnabled(state) {
+export function isTimezoneEnabled(state: GlobalState) {
     const {config} = state.entities.general;
     return config.ExperimentalTimezone === 'true';
 }
diff --git a/src/selectors/entities/users.ts b/src/selectors/entities/users.ts
index fd02216f0..12c6925ae 100644
--- a/src/selectors/entities/users.ts
+++ b/src/selectors/entities/users.ts
@@ -11,7 +11,7 @@ import {UserProfile} from 'types/users';
 import {Reaction} from 'types/reactions';
 import {Team} from 'types/teams';
 import {Channel} from 'types/channels';
-import {RelationOneToOne, RelationOneToMany, IDMappedObjects, UsernameMappedObjects, EmailMappedObjects, $ID, $Username, $Email} from 'types/utilities';
+import {RelationOneToOne, RelationOneToMany, IDMappedObjects, UsernameMappedObjects, EmailMappedObjects, $ID, $Username, $Email, Dictionary} from 'types/utilities';
 type Filters = {
     role?: string;
     inactive?: boolean;
@@ -52,10 +52,10 @@ export function getUser(state: GlobalState, id: $ID<UserProfile>): UserProfile {
     return state.entities.users.profiles[id];
 }
 
-export const getUsersByUsername: (GlobalState) => UsernameMappedObjects<UserProfile> = createSelector(
+export const getUsersByUsername: (a: GlobalState) => UsernameMappedObjects<UserProfile> = createSelector(
     getUsers,
     (users) => {
-        const usersByUsername = {};
+        const usersByUsername: Dictionary<UserProfile> = {};
 
         for (const id in users) {
             if (users.hasOwnProperty(id)) {
@@ -72,10 +72,10 @@ export function getUserByUsername(state: GlobalState, username: $Username<UserPr
     return getUsersByUsername(state)[username];
 }
 
-export const getUsersByEmail: (GlobalState) => EmailMappedObjects<UserProfile> = createSelector(
+export const getUsersByEmail: (a: GlobalState) => EmailMappedObjects<UserProfile> = createSelector(
     getUsers,
     (users) => {
-        const usersByEmail = {};
+        const usersByEmail: Dictionary<UserProfile> = {};
 
         for (const user of Object.keys(users).map((key) => users[key])) {
             usersByEmail[user.email] = user;
@@ -89,7 +89,7 @@ export function getUserByEmail(state: GlobalState, email: $Email<UserProfile>):
     return getUsersByEmail(state)[email];
 }
 
-export const isCurrentUserSystemAdmin: (GlobalState) => boolean = createSelector(
+export const isCurrentUserSystemAdmin: (a: GlobalState) => boolean = createSelector(
     getCurrentUser,
     (user) => {
         const roles = user.roles || '';
@@ -113,11 +113,14 @@ export const getCurrentUserRoles: (a: GlobalState) => UserProfile['roles'] = cre
     return roles.trim();
 }
 );
-export const getCurrentUserMentionKeys: (a: GlobalState) => Array<{
+
+export type UserMentionKey= {
     key: string;
     caseSensitive?: boolean;
-}> = createSelector(getCurrentUser, (user: UserProfile) => {
-    let keys: {key;caseSensitive?}[] = [];
+}
+
+export const getCurrentUserMentionKeys: (a: GlobalState) => Array<UserMentionKey> = createSelector(getCurrentUser, (user: UserProfile) => {
+    let keys: UserMentionKey[] = [];
 
     if (!user || !user.notify_props) {
         return keys;
@@ -203,7 +206,7 @@ function sortAndInjectProfiles(profiles: IDMappedObjects<UserProfile>, profileSe
 
 export const getProfiles: (a: GlobalState, b: Filters) => Array<UserProfile> = createSelector(
     getUsers,
-    (state, filters) => filters,
+    (state: GlobalState, filters: Filters) => filters,
     (profiles, filters) => {
         return sortAndInjectProfiles(filterProfiles(profiles, filters), PROFILE_SET_ALL);
     }
@@ -227,7 +230,7 @@ function filterProfiles(profiles: IDMappedObjects<UserProfile>, filters?: Filter
     return users.reduce((acc, user) => {
         acc[user.id] = user;
         return acc;
-    }, {});
+    }, {} as IDMappedObjects<UserProfile>);
 }
 
 export const getProfilesInCurrentChannel: (a: GlobalState) => Array<UserProfile> = createSelector(
@@ -257,8 +260,8 @@ export const getProfilesInCurrentTeam: (a: GlobalState) => Array<UserProfile> =
 export const getProfilesInTeam: (a: GlobalState, b: $ID<Team>) => Array<UserProfile> = createSelector(
     getUsers,
     getUserIdsInTeams,
-    (state, teamId) => teamId,
-    (state, teamId, filters) => filters,
+    (state: GlobalState, teamId: string) => teamId,
+    (state: GlobalState, teamId, filters) => filters,
     (profiles, usersInTeams, teamId, filters) => {
         return sortAndInjectProfiles(filterProfiles(profiles, filters), usersInTeams[teamId] || new Set());
     }
@@ -275,7 +278,7 @@ export const getProfilesNotInCurrentTeam: (a: GlobalState) => Array<UserProfile>
 export const getProfilesWithoutTeam: (a: GlobalState, filters?: Filters) => Array<UserProfile> = createSelector(
     getUsers,
     getUserIdsWithoutTeam,
-    (state, filters) => filters,
+    (state: GlobalState, filters: Filters) => filters,
     (profiles, withoutTeamProfileSet, filters) => {
         return sortAndInjectProfiles(filterProfiles(profiles, filters), withoutTeamProfileSet);
     }
@@ -375,7 +378,7 @@ export const shouldShowTermsOfService: (a: GlobalState) => boolean = createSelec
         const acceptedAt = user ? user.terms_of_service_create_at : 0;
 
         const featureEnabled = license.IsLicensed === 'true' && config.EnableCustomTermsOfService === 'true';
-        const reacceptanceTime = config.CustomTermsOfServiceReAcceptancePeriod * 1000 * 60 * 60 * 24;
+        const reacceptanceTime = parseInt(config.CustomTermsOfServiceReAcceptancePeriod!, 10) * 1000 * 60 * 60 * 24;
         const timeElapsed = new Date().getTime() - acceptedAt;
         return Boolean(user && featureEnabled && (config.CustomTermsOfServiceId !== acceptedTermsId || timeElapsed > reacceptanceTime));
     }
@@ -398,7 +401,7 @@ export const getUsersInVisibleDMs: (a: GlobalState) => Array<UserProfile> = crea
 export function makeGetProfilesForReactions(): (a: GlobalState, b: Array<Reaction>) => Array<UserProfile> {
     return createSelector(
         getUsers,
-        (state, reactions) => reactions,
+        (state: GlobalState, reactions: Array<Reaction>) => reactions,
         (users, reactions) => {
             const profiles: UserProfile[] = [];
             reactions.forEach((r) => {
@@ -415,7 +418,7 @@ export function makeGetProfilesInChannel(): (a: GlobalState, b: $ID<Channel>, c:
     return createSelector(
         getUsers,
         getUserIdsInChannels,
-        (state, channelId) => channelId,
+        (state: GlobalState, channelId: string) => channelId,
         (state, channelId, skipInactive) => skipInactive,
         (users, userIds, channelId, skipInactive = false) => {
             const userIdsInChannel = userIds[channelId];
@@ -433,7 +436,7 @@ export function makeGetProfilesNotInChannel(): (a: GlobalState, b: $ID<Channel>,
     return createSelector(
         getUsers,
         getUserIdsNotInChannels,
-        (state, channelId) => channelId,
+        (state: GlobalState, channelId: string) => channelId,
         (state, channelId, skipInactive) => skipInactive,
         (users, userIds, channelId, skipInactive = false) => {
             const userIdsInChannel = userIds[channelId];
@@ -451,9 +454,9 @@ export function makeGetProfilesByIdsAndUsernames(): (a: GlobalState, b: {allUser
     return createSelector(
         getUsers,
         getUsersByUsername,
-        (state, props) => props.allUserIds,
+        (state: GlobalState, props: {allUserIds: Array<$ID<UserProfile>>; allUsernames: Array<$Username<UserProfile>>}) => props.allUserIds,
         (state, props) => props.allUsernames,
-        (allProfilesById, allProfilesByUsername, allUserIds, allUsernames) => {
+        (allProfilesById: Dictionary<UserProfile>, allProfilesByUsername: Dictionary<UserProfile>, allUserIds: Array<string>, allUsernames: Array<string>) => {
             const userProfiles: UserProfile[] = [];
 
             if (allUserIds && allUserIds.length > 0) {
@@ -483,11 +486,11 @@ export function makeGetProfilesByIdsAndUsernames(): (a: GlobalState, b: {allUser
 
 export function makeGetDisplayName(): (a: GlobalState, b: $ID<UserProfile>, c: boolean) => string {
     return createSelector(
-        (state, userId) => getUser(state, userId),
+        (state: GlobalState, userId: string) => getUser(state, userId),
         getTeammateNameDisplaySetting,
         (state, _, useFallbackUsername = true) => useFallbackUsername,
         (user, teammateNameDisplaySetting, useFallbackUsername) => {
-            return displayUsername(user, teammateNameDisplaySetting, useFallbackUsername);
+            return displayUsername(user, teammateNameDisplaySetting!, useFallbackUsername);
         }
     );
 }
diff --git a/src/selectors/errors.ts b/src/selectors/errors.ts
index 718a21b81..cb95ce77a 100644
--- a/src/selectors/errors.ts
+++ b/src/selectors/errors.ts
@@ -1,6 +1,8 @@
 // Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
 // See LICENSE.txt for license information.
 
-export function getDisplayableErrors(state) {
+import {GlobalState} from 'types/store';
+
+export function getDisplayableErrors(state: GlobalState) {
     return state.errors.filter((error) => error.displayable);
 }
diff --git a/src/store/configureStore.dev.ts b/src/store/configureStore.dev.ts
index 30367ad34..2cbd7793a 100644
--- a/src/store/configureStore.dev.ts
+++ b/src/store/configureStore.dev.ts
@@ -3,10 +3,10 @@
 
 /* eslint-disable no-undefined */
 import * as redux from 'redux';
-import devTools from 'remote-redux-devtools';
 import {createOfflineReducer, networkStatusChangedAction, offlineCompose} from 'redux-offline';
 import defaultOfflineConfig from 'redux-offline/lib/defaults';
 import reducerRegistry from './reducer_registry';
+import devTools from 'remote-redux-devtools';
 
 const windowAny = window as any;
 
@@ -25,6 +25,8 @@ import deepFreezeAndThrowOnMutation from 'utils/deep_freeze';
 import initialState from './initial_state';
 import {offlineConfig, createReducer} from './helpers';
 import {createMiddleware} from './middleware';
+import {Reducer, Action} from 'types/actions';
+import {GlobalState} from 'types/store';
 
 /**
  * Configures and constructs the redux store. Accepts the following parameters:
@@ -37,7 +39,7 @@ import {createMiddleware} from './middleware';
  *     enableBuffer - bool - default = true - If true, the store will buffer all actions until offline state rehydration occurs.
  *     enableThunk - bool - default = true - If true, include the thunk middleware automatically. If false, thunk must be provided as part of additionalMiddleware.
  */
-export default function configureServiceStore(preloadedState, appReducer, userOfflineConfig, getAppReducer, clientOptions) {
+export default function configureServiceStore(preloadedState: any, appReducer: any, userOfflineConfig: any, getAppReducer: any, clientOptions: any) {
     const baseOfflineConfig = Object.assign({}, defaultOfflineConfig, offlineConfig, userOfflineConfig);
     const baseState = Object.assign({}, initialState, preloadedState);
 
@@ -52,7 +54,7 @@ export default function configureServiceStore(preloadedState, appReducer, userOf
         )
     );
 
-    reducerRegistry.setChangeListener((reducers) => {
+    reducerRegistry.setChangeListener((reducers: any) => {
         store.replaceReducer(createOfflineReducer(createDevReducer(baseState, reducers)));
     });
 
@@ -62,7 +64,7 @@ export default function configureServiceStore(preloadedState, appReducer, userOf
     }
 
     if (baseOfflineConfig.detectNetwork) {
-        baseOfflineConfig.detectNetwork((online) => {
+        baseOfflineConfig.detectNetwork((online: boolean) => {
             store.dispatch(networkStatusChangedAction(online));
         });
     }
@@ -82,12 +84,12 @@ export default function configureServiceStore(preloadedState, appReducer, userOf
     return store;
 }
 
-function createDevReducer(baseState, ...reducers) {
+function createDevReducer(baseState: any, ...reducers: any) {
     return enableFreezing(createReducer(baseState, ...reducers));
 }
 
-function enableFreezing(reducer) {
-    return (state, action) => {
+function enableFreezing(reducer: Reducer) {
+    return (state: GlobalState, action: Action) => {
         const nextState = reducer(state, action);
 
         if (nextState !== state) {
diff --git a/src/store/configureStore.prod.ts b/src/store/configureStore.prod.ts
index 4318c3fcf..f1d456386 100644
--- a/src/store/configureStore.prod.ts
+++ b/src/store/configureStore.prod.ts
@@ -2,8 +2,6 @@
 // See LICENSE.txt for license information.
 
 import * as redux from 'redux';
-import {createOfflineReducer, networkStatusChangedAction, offlineCompose} from 'redux-offline';
-import defaultOfflineConfig from 'redux-offline/lib/defaults';
 import reducerRegistry from './reducer_registry';
 
 import serviceReducer from '../reducers';
@@ -12,6 +10,9 @@ import {offlineConfig, createReducer} from './helpers';
 import initialState from './initial_state';
 import {createMiddleware} from './middleware';
 
+import {createOfflineReducer, networkStatusChangedAction, offlineCompose} from 'redux-offline';
+import defaultOfflineConfig from 'redux-offline/lib/defaults';
+
 /**
  * Configures and constructs the redux store. Accepts the following parameters:
  * preloadedState - Any preloaded state to be applied to the store after it is initially configured.
@@ -23,13 +24,13 @@ import {createMiddleware} from './middleware';
  *     enableBuffer - bool - default = true - If true, the store will buffer all actions until offline state rehydration occurs.
  *     enableThunk - bool - default = true - If true, include the thunk middleware automatically. If false, thunk must be provided as part of additionalMiddleware.
  */
-export default function configureOfflineServiceStore(preloadedState, appReducer, userOfflineConfig, getAppReducer, clientOptions = {}) {
+export default function configureOfflineServiceStore(preloadedState: any, appReducer: any, userOfflineConfig: any, getAppReducer: any, clientOptions = {}) {
     const baseState = Object.assign({}, initialState, preloadedState);
 
     const baseOfflineConfig = Object.assign({}, defaultOfflineConfig, offlineConfig, userOfflineConfig);
 
     const store = redux.createStore(
-        createOfflineReducer(createReducer(baseState, serviceReducer, appReducer)),
+        createOfflineReducer(createReducer(baseState, serviceReducer as any, appReducer)),
         baseState,
         offlineCompose(baseOfflineConfig)(
             createMiddleware(clientOptions),
@@ -37,7 +38,7 @@ export default function configureOfflineServiceStore(preloadedState, appReducer,
         )
     );
 
-    reducerRegistry.setChangeListener((reducers) => {
+    reducerRegistry.setChangeListener((reducers: any) => {
         store.replaceReducer(createOfflineReducer(createReducer(baseState, reducers)));
     });
 
@@ -47,7 +48,7 @@ export default function configureOfflineServiceStore(preloadedState, appReducer,
     }
 
     if (baseOfflineConfig.detectNetwork) {
-        baseOfflineConfig.detectNetwork((online) => {
+        baseOfflineConfig.detectNetwork((online: boolean) => {
             store.dispatch(networkStatusChangedAction(online));
         });
     }
diff --git a/src/store/helpers.ts b/src/store/helpers.ts
index 8cb1b1aa5..3ee39ed6e 100644
--- a/src/store/helpers.ts
+++ b/src/store/helpers.ts
@@ -3,19 +3,19 @@
 import {combineReducers} from 'redux';
 import {General} from '../constants';
 import reducerRegistry from './reducer_registry';
-import {enableBatching} from 'types/actions';
+import {enableBatching, Action, Reducer} from 'types/actions';
 export const offlineConfig = {
-    effect: (effect, action) => {
+    effect: (effect: Function, action: Action) => {
         if (typeof effect !== 'function') {
             throw new Error('Offline Action: effect must be a function.');
-        } else if (!action.meta.offline.commit) {
+        } else if (!('meta' in action && action.meta && action.meta.offline.commit)) {
             throw new Error('Offline Action: commit action must be present.');
         }
 
         return effect();
     },
-    discard: (error, action, retries) => {
-        if (action.meta && action.meta.offline.hasOwnProperty('maxRetry')) {
+    discard: (error: Error, action: Action, retries: number) => {
+        if ('meta' in action && action.meta && action.meta.offline.hasOwnProperty('maxRetry')) {
             return retries >= action.meta.offline.maxRetry;
         }
 
@@ -23,19 +23,19 @@ export const offlineConfig = {
     },
 };
 
-export function createReducer(baseState, ...reducers) {
+export function createReducer(baseState: any, ...reducers: Reducer[]) {
     reducerRegistry.setReducers(Object.assign({}, ...reducers));
     const baseReducer = combineReducers(reducerRegistry.getReducers());
 
     // Root reducer wrapper that listens for reset events.
     // Returns whatever is passed for the data property
     // as the new state.
-    function offlineReducer(state = {}, action) {
-        if (action.type === General.OFFLINE_STORE_RESET) {
+    function offlineReducer(state = {}, action: Action) {
+        if ('type' in action && 'data' in action && action.type === General.OFFLINE_STORE_RESET) {
             return baseReducer(action.data || baseState, action);
         }
 
-        return baseReducer(state, action);
+        return baseReducer(state, action as any);
     }
 
     return enableBatching(offlineReducer);
diff --git a/src/store/initial_state.ts b/src/store/initial_state.ts
index d3ffea14c..47d582a69 100644
--- a/src/store/initial_state.ts
+++ b/src/store/initial_state.ts
@@ -66,6 +66,9 @@ const state: GlobalState = {
         preferences: {
             myPreferences: {},
         },
+        bots: {
+            accounts: {},
+        },
         admin: {
             logs: [],
             audits: {},
@@ -74,6 +77,8 @@ const state: GlobalState = {
             complianceReports: {},
             ldapGroups: {},
             ldapGroupsCount: 0,
+            userAccessTokens: [],
+            clusterInfo: {},
         },
         jobs: {
             jobs: {},
@@ -89,6 +94,9 @@ const state: GlobalState = {
             systemCommands: {},
             commands: {},
         },
+        plugins: {
+            marketplacePlugins: [],
+        },
         files: {
             files: {},
             fileIdsByPostId: {},
diff --git a/src/store/middleware.ts b/src/store/middleware.ts
index c07d75255..88a1ca420 100644
--- a/src/store/middleware.ts
+++ b/src/store/middleware.ts
@@ -1,14 +1,16 @@
 // Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
 // See LICENSE.txt for license information.
+import thunk, {ThunkMiddleware} from 'redux-thunk';
+
 import createActionBuffer from 'redux-action-buffer';
 import {REHYDRATE} from 'redux-persist/constants';
-import thunk, {ThunkMiddleware} from 'redux-thunk';
+
 const defaultOptions = {
     additionalMiddleware: [],
     enableBuffer: true,
     enableThunk: true,
 };
-export function createMiddleware(clientOptions): ThunkMiddleware[] {
+export function createMiddleware(clientOptions: any): ThunkMiddleware[] {
     const options = Object.assign({}, defaultOptions, clientOptions);
     const {
         additionalMiddleware,
diff --git a/src/store/reducer_registry.ts b/src/store/reducer_registry.ts
index 057a7620d..0b8ccde87 100644
--- a/src/store/reducer_registry.ts
+++ b/src/store/reducer_registry.ts
@@ -1,12 +1,15 @@
 // Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
 // See LICENSE.txt for license information.
 
+import {Reducer} from 'types/actions';
+import {Dictionary} from 'types/utilities';
+
 // Based on http://nicolasgallagher.com/redux-modules-and-code-splitting/
 export class ReducerRegistry {
     emitChange?: Function;
-    reducers = {};
+    reducers: Dictionary<Reducer> = {};
 
-    setReducers = (reducers) => {
+    setReducers = (reducers: Dictionary<Reducer>) => {
         this.reducers = reducers;
     }
 
@@ -14,14 +17,14 @@ export class ReducerRegistry {
         return {...this.reducers};
     }
 
-    register = (name, reducer) => {
+    register = (name: string, reducer: Reducer) => {
         this.reducers = {...this.reducers, [name]: reducer};
         if (this.emitChange) {
             this.emitChange(this.getReducers());
         }
     }
 
-    setChangeListener = (listener) => {
+    setChangeListener = (listener: Function) => {
         this.emitChange = listener;
     }
 }
diff --git a/src/types/actions.ts b/src/types/actions.ts
index 90af666bd..8a2507dd9 100644
--- a/src/types/actions.ts
+++ b/src/types/actions.ts
@@ -17,7 +17,7 @@ export type GenericAction = {
     timestamp?: number;
     [extraProps: string]: any;
 };
-type Thunk = (b: DispatchFunc, a: GetStateFunc) => Promise<ActionResult> | ActionResult;
+export type Thunk = (b: DispatchFunc, a: GetStateFunc) => Promise<ActionResult> | ActionResult;
 
 type BatchAction = {
     type: 'BATCHING_REDUCER.BATCH';
@@ -44,32 +44,16 @@ export function batchActions(actions: Action[], type = BATCH) {
     return {type, meta: {batch: true}, payload: actions};
 }
 
-export function enableBatching(reduce) {
+export type Reducer<S = any, A extends Action = Action> = (
+    state: S | undefined,
+    action: A
+  ) => S
+
+export function enableBatching<S>(reduce: Reducer<S>): Reducer<S> {
     return function batchingReducer(state, action) {
-        if (action && action.meta && action.meta.batch) {
+        if (action && 'meta' in action && action.meta.batch) {
             return action.payload.reduce(batchingReducer, state);
         }
         return reduce(state, action);
     };
 }
-
-export function batchDispatchMiddleware(store_) {
-    function dispatchChildActions(store, action) {
-        if (action.meta && action.meta.batch) {
-            action.payload.forEach((childAction) => {
-                dispatchChildActions(store, childAction);
-            });
-        } else {
-            store.dispatch(action);
-        }
-    }
-
-    return (next) => {
-        return (action) => {
-            if (action && action.meta && action.meta.batch) {
-                dispatchChildActions(store_, action);
-            }
-            return next(action);
-        };
-    };
-}
diff --git a/src/types/admin.ts b/src/types/admin.ts
index 5d4f8c7e7..e808dad57 100644
--- a/src/types/admin.ts
+++ b/src/types/admin.ts
@@ -8,4 +8,6 @@ export type AdminState = {
     complianceReports: any;
     ldapGroups: any;
     ldapGroupsCount: number;
+    userAccessTokens: any[];
+    clusterInfo: any;
 };
diff --git a/src/types/bots.ts b/src/types/bots.ts
new file mode 100644
index 000000000..2a3e17c2a
--- /dev/null
+++ b/src/types/bots.ts
@@ -0,0 +1,20 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+export type Bot = {
+	user_id: string ;
+	username: string ;
+	display_name?: string ;
+	description?: string ;
+	owner_id: string ;
+	create_at: number ;
+	update_at: number ;
+	delete_at: number ;
+}
+
+// BotPatch is a description of what fields to update on an existing bot.
+export type BotPatch = {
+	username: string;
+	display_name: string;
+    description: string;
+}
\ No newline at end of file
diff --git a/src/types/client4.ts b/src/types/client4.ts
index d33e8fa94..fcee74987 100644
--- a/src/types/client4.ts
+++ b/src/types/client4.ts
@@ -24,4 +24,10 @@ export type ErrorApi = {
     url: string;
 };
 export type Client4Error = ErrorOffline | ErrorInvalidResponse | ErrorApi;
-export type Options = { headers: {[x: string]: string}; method?: string;url?: string; credentials?: 'omit' | 'same-origin' | 'include'};
+export type Options = {
+    headers?: { [x: string]: string };
+    method?: string;
+    url?: string;
+    credentials?: 'omit' | 'same-origin' | 'include';
+    body?: any;
+};
diff --git a/src/types/config.ts b/src/types/config.ts
new file mode 100644
index 000000000..2bf279345
--- /dev/null
+++ b/src/types/config.ts
@@ -0,0 +1,162 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+export type Config = {
+    AboutLink: string;
+    AllowBannerDismissal: string;
+    AllowCustomThemes: string;
+    AllowedThemes: string;
+    AndroidAppDownloadLink: string;
+    AndroidLatestVersion: string;
+    AndroidMinVersion: string;
+    AppDownloadLink: string;
+    AvailableLocales: string;
+    BannerColor: string;
+    BannerText: string;
+    BannerTextColor: string;
+    BuildDate: string;
+    BuildEnterpriseReady: string;
+    BuildHash: string;
+    BuildHashEnterprise: string;
+    BuildNumber: string;
+    CloseUnusedDirectMessages: string;
+    CustomBrandText: string;
+    CustomDescriptionText: string;
+    CustomTermsOfServiceId: string;
+    CustomTermsOfServiceReAcceptancePeriod: string;
+    CustomUrlSchemes: string;
+    DataRetentionEnableFileDeletion: string;
+    DataRetentionEnableMessageDeletion: string;
+    DataRetentionFileRetentionDays: string;
+    DataRetentionMessageRetentionDays: string;
+    DefaultClientLocale: string;
+    DefaultTheme: string;
+    DesktopLatestVersion: string;
+    DesktopMinVersion: string;
+    DiagnosticId: string;
+    DiagnosticsEnabled: string;
+    EmailLoginButtonBorderColor: string;
+    EmailLoginButtonColor: string;
+    EmailLoginButtonTextColor: string;
+    EmailNotificationContentsType: string;
+    EnableBanner: string;
+    EnableBotAccountCreation: string;
+    EnableChannelViewedMessages: string;
+    EnableCluster: string;
+    EnableCommands: string;
+    EnableCompliance: string;
+    EnableConfirmNotificationsToChannel: string;
+    EnableCustomBrand: string;
+    EnableCustomEmoji: string;
+    EnableCustomTermsOfService: string;
+    EnableDeveloper: string;
+    EnableDiagnostics: string;
+    EnableEmailBatching: string;
+    EnableEmailInvitations: string;
+    EnableEmojiPicker: string;
+    EnableFileAttachments: string;
+    EnableGifPicker: string;
+    EnableGuestAccounts: string;
+    EnableIncomingWebhooks: string;
+    EnableLatex: string;
+    EnableLdap: string;
+    EnableLinkPreviews: string;
+    EnableMarketplace: string;
+    EnableMetrics: string;
+    EnableMobileFileDownload: string;
+    EnableMobileFileUpload: string;
+    EnableMultifactorAuthentication: string;
+    EnableOAuthServiceProvider: string;
+    EnableOpenServer: string;
+    EnableOutgoingWebhooks: string;
+    EnablePostIconOverride: string;
+    EnablePostUsernameOverride: string;
+    EnablePreviewFeatures: string;
+    EnablePreviewModeBanner: string;
+    EnablePublicLink: string;
+    EnableSaml: string;
+    EnableSignInWithEmail: string;
+    EnableSignInWithUsername: string;
+    EnableSignUpWithEmail: string;
+    EnableSignUpWithGitLab: string;
+    EnableSignUpWithGoogle: string;
+    EnableSignUpWithOffice365: string;
+    EnableSVGs: string;
+    EnableTesting: string;
+    EnableThemeSelection: string;
+    EnableTutorial: string;
+    EnableUserAccessTokens: string;
+    EnableUserCreation: string;
+    EnableUserDeactivation: string;
+    EnableUserTypingMessages: string;
+    EnableXToLeaveChannelsFromLHS: string;
+    EnforceMultifactorAuthentication: string;
+    ExperimentalChannelOrganization: string;
+    ExperimentalClientSideCertCheck: string;
+    ExperimentalClientSideCertEnable: string;
+    ExperimentalEnableAuthenticationTransfer: string;
+    ExperimentalEnableAutomaticReplies: string;
+    ExperimentalEnableClickToReply: string;
+    ExperimentalEnableDefaultChannelLeaveJoinMessages: string;
+    ExperimentalEnablePostMetadata: string;
+    ExperimentalGroupUnreadChannels: string;
+    ExperimentalHideTownSquareinLHS: string;
+    ExperimentalPrimaryTeam: string;
+    ExperimentalTimezone: string;
+    ExperimentalTownSquareIsReadOnly: string;
+    ExperimentalViewArchivedChannels: string;
+    GfycatApiKey: string;
+    GfycatApiSecret: string;
+    GoogleDeveloperKey: string;
+    GuestAccountsEnforceMultifactorAuthentication: string;
+    HasImageProxy: string;
+    HelpLink: string;
+    IosAppDownloadLink: string;
+    IosLatestVersion: string;
+    IosMinVersion: string;
+    LdapFirstNameAttributeSet: string;
+    LdapLastNameAttributeSet: string;
+    LdapLoginButtonBorderColor: string;
+    LdapLoginButtonColor: string;
+    LdapLoginButtonTextColor: string;
+    LdapLoginFieldName: string;
+    LdapNicknameAttributeSet: string;
+    LdapPositionAttributeSet: string;
+    MaxFileSize: string;
+    MaxNotificationsPerChannel: string;
+    MinimumHashtagLength: string;
+    PasswordMinimumLength: string;
+    PasswordRequireLowercase: string;
+    PasswordRequireNumber: string;
+    PasswordRequireSymbol: string;
+    PasswordRequireUppercase: string;
+    PluginsEnabled: string;
+    PostEditTimeLimit: string;
+    PrivacyPolicyLink: string;
+    ReportAProblemLink: string;
+    RequireEmailVerification: string;
+    RestrictDirectMessage: string;
+    RunJobs: string;
+    SamlFirstNameAttributeSet: string;
+    SamlLastNameAttributeSet: string;
+    SamlLoginButtonBorderColor: string;
+    SamlLoginButtonColor: string;
+    SamlLoginButtonText: string;
+    SamlLoginButtonTextColor: string;
+    SamlNicknameAttributeSet: string;
+    SamlPositionAttributeSet: string;
+    SendEmailNotifications: string;
+    SendPushNotifications: string;
+    ShowEmailAddress: string;
+    SiteName: string;
+    SiteURL: string;
+    SQLDriverName: string;
+    SupportEmail: string;
+    TeammateNameDisplay: string;
+    TermsOfServiceLink: string;
+    TimeBetweenUserTypingUpdatesMilliseconds: string;
+    Version: string;
+    WebsocketPort: string;
+    WebsocketSecurePort: string;
+    WebsocketURL: string;
+};
diff --git a/src/types/files.ts b/src/types/files.ts
index 7e5d13001..38cf1a639 100644
--- a/src/types/files.ts
+++ b/src/types/files.ts
@@ -1,5 +1,8 @@
 // Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
 // See LICENSE.txt for license information.
+
+import {Dictionary} from './utilities';
+
 export type FileInfo = {
     id: string;
     user_id: string;
@@ -16,10 +19,12 @@ export type FileInfo = {
     clientId: string;
 };
 export type FilesState = {
-    files: {
-        [x: string]: FileInfo;
-    };
-    fileIdsByPostId: {
-        [x: string]: Array<string>;
-    };
+    files: Dictionary<FileInfo>;
+    fileIdsByPostId: Dictionary<Array<string>>;
+    filePublicLink?: string;
 };
+
+export type FileUploadResponse = {
+    file_infos: FileInfo[];
+    client_ids: string[];
+}
\ No newline at end of file
diff --git a/src/types/general.ts b/src/types/general.ts
index c76f3d0b1..c51e0b7de 100644
--- a/src/types/general.ts
+++ b/src/types/general.ts
@@ -1,9 +1,12 @@
 // Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
 // See LICENSE.txt for license information.
+
+import {Config} from './config';
+
 export type GeneralState = {
     appState: boolean;
     credentials: any;
-    config: any;
+    config: Partial<Config>;
     dataRetentionPolicy: any;
     deviceToken: string;
     license: any;
diff --git a/src/types/index.ts b/src/types/index.ts
index 42fd8fabf..1ecf0d089 100644
--- a/src/types/index.ts
+++ b/src/types/index.ts
@@ -25,11 +25,17 @@ import * as teams from './teams';
 import * as typing from './typing';
 import * as utilities from './utilities';
 import * as users from './users';
+import * as bots from './bots';
+import * as plugins from './plugins';
+import * as config from './config';
 
 export {
     admin,
+    config,
     actions,
     alerts,
+    bots,
+    plugins,
     store,
     channels,
     errors,
diff --git a/src/types/integrations.ts b/src/types/integrations.ts
index cf819ac8f..92dd8755e 100644
--- a/src/types/integrations.ts
+++ b/src/types/integrations.ts
@@ -23,7 +23,7 @@ export type OutgoingWebhook = {
     delete_at: number;
     creator_id: string;
     channel_id: string;
-    teamId: string;
+    team_id: string;
     trigger_words: Array<string>;
     trigger_when: number;
     callback_urls: Array<string>;
diff --git a/src/types/module.d.ts b/src/types/module.d.ts
new file mode 100644
index 000000000..3dd9c11aa
--- /dev/null
+++ b/src/types/module.d.ts
@@ -0,0 +1,9 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+declare module 'gfycat-sdk';
+declare module 'redux-offline';
+declare module 'redux-offline/lib/defaults';
+declare module 'remote-redux-devtools';
+declare module 'redux-persist';
+declare module 'redux-persist/constants';
+declare module 'redux-action-buffer';
\ No newline at end of file
diff --git a/src/types/plugins.ts b/src/types/plugins.ts
new file mode 100644
index 000000000..052ac0d7b
--- /dev/null
+++ b/src/types/plugins.ts
@@ -0,0 +1,15 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+export type MarketplacePlugin = {
+    homepage_url: string;
+    download_url: string;
+    manifest: {
+        id: string;
+        name: string;
+        description: string;
+        version: string;
+        minServerVersion: string;
+    };
+    installed_version: string;
+}
diff --git a/src/types/posts.ts b/src/types/posts.ts
index 4a0b4c7a4..8b806097c 100644
--- a/src/types/posts.ts
+++ b/src/types/posts.ts
@@ -77,7 +77,7 @@ export type PostWithFormatData = Post & {
     isFirstReply: boolean;
     isLastReply: boolean;
     previousPostIsComment: boolean;
-    commentedOnPost: Post;
+    commentedOnPost?: Post;
     consecutivePostByUser: boolean;
     replyCount: number;
     isCommentMention: boolean;
@@ -86,32 +86,27 @@ export type PostWithFormatData = Post & {
 
 export type PostOrderBlock = {
     order: Array<string>;
-    recent: boolean;
-    oldest: boolean;
+    recent?: boolean;
+    oldest?: boolean;
+};
+
+export type MessageHistory = {
+    messages: Array<string>;
+    index: {
+        post: number;
+        comment: number;
+    };
 };
 
 export type PostsState = {
     posts: IDMappedObjects<Post>;
-    postsInChannel: {
-        [x: string]: Array<PostOrderBlock>;
-    };
+    postsInChannel: Dictionary<Array<PostOrderBlock>>;
     postsInThread: RelationOneToMany<Post, Post>;
-    reactions: RelationOneToOne<
-        Post,
-        {
-            [x: string]: Reaction;
-        }
-        >;
+    reactions: RelationOneToOne<Post, Dictionary<Reaction>>;
     openGraph: RelationOneToOne<Post, any>;
     pendingPostIds: Array<string>;
     selectedPostId: string;
     currentFocusedPostId: string;
-    messagesHistory: {
-        messages: Array<string>;
-        index: {
-            post: number;
-            comment: number;
-        };
-    };
-    expandedURLs: { [x: string]: string};
+    messagesHistory: MessageHistory;
+    expandedURLs: Dictionary<string>;
 };
diff --git a/src/types/search.ts b/src/types/search.ts
index 97ba00d91..8b9888591 100644
--- a/src/types/search.ts
+++ b/src/types/search.ts
@@ -1,9 +1,11 @@
 // Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
 // See LICENSE.txt for license information.
+
 export type Search = {
     terms: string;
     isOrSearch: boolean;
 };
+
 export type SearchState = {
     current: any;
     results: Array<string>;
@@ -14,3 +16,12 @@ export type SearchState = {
         [x: string]: Array<string>;
     };
 };
+
+export type SearchParameter = {
+	terms: string;
+	is_or_search: boolean;
+	time_zone_offset?: number;
+	page: number;
+	per_page: number;
+	include_deleted_channels: boolean;
+}
\ No newline at end of file
diff --git a/src/types/store.ts b/src/types/store.ts
index f510a51df..266e7fb9c 100644
--- a/src/types/store.ts
+++ b/src/types/store.ts
@@ -18,6 +18,10 @@ import {GroupsState} from './groups';
 import {ChannelsRequestsStatuses, GeneralRequestsStatuses, PostsRequestsStatuses, TeamsRequestsStatuses, UsersRequestsStatuses, PreferencesRequestsStatuses, AdminRequestsStatuses, FilesRequestsStatuses, IntegrationsRequestsStatuses, RolesRequestsStatuses, SchemesRequestsStatuses, GroupsRequestsStatuses, JobsRequestsStatuses, SearchRequestsStatuses} from './requests';
 import {Role} from './roles';
 import {PreferenceType} from './preferences';
+import {MarketplacePlugin} from './plugins';
+import {Bot} from './bots';
+import {Dictionary} from './utilities';
+
 export type GlobalState = {
     entities: {
         general: GeneralState;
@@ -25,6 +29,9 @@ export type GlobalState = {
         teams: TeamsState;
         channels: ChannelsState;
         posts: PostsState;
+        bots: {
+            accounts: Dictionary<Bot>;
+        };
         preferences: {
             myPreferences: {
                 [x: string]: PreferenceType;
@@ -48,6 +55,9 @@ export type GlobalState = {
         };
         schemes: SchemesState;
         gifs: any;
+        plugins: {
+            marketplacePlugins: Array<MarketplacePlugin>;
+        };
         groups: GroupsState;
     };
     errors: Array<any>;
diff --git a/src/types/teams.ts b/src/types/teams.ts
index dbc536cd2..38a2eb5a1 100644
--- a/src/types/teams.ts
+++ b/src/types/teams.ts
@@ -1,5 +1,8 @@
 // Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
 // See LICENSE.txt for license information.
+
+import {Dictionary} from './utilities';
+
 export type TeamMembership = {
     mention_count: number;
     msg_count: number;
@@ -10,7 +13,9 @@ export type TeamMembership = {
     scheme_user: boolean;
     scheme_admin: boolean;
 };
+
 export type TeamType = 'O' | 'I';
+
 export type Team = {
     id: string;
     create_at: number;
@@ -28,14 +33,11 @@ export type Team = {
     scheme_id: string;
     group_constrained: boolean;
 };
+
 export type TeamsState = {
     currentTeamId: string;
-    teams: {
-        [x: string]: Team;
-    };
-    myMembers: {
-        [x: string]: TeamMembership;
-    };
+    teams: Dictionary<Team>;
+    myMembers: Dictionary<TeamMembership>;
     membersInTeam: any;
     stats: any;
     groupsAssociatedToTeam: any;
diff --git a/src/types/users.ts b/src/types/users.ts
index f613ff85e..9633406a5 100644
--- a/src/types/users.ts
+++ b/src/types/users.ts
@@ -44,7 +44,7 @@ export type UsersState = {
     profiles: IDMappedObjects<UserProfile>;
     profilesInTeam: RelationOneToMany<Team, UserProfile>;
     profilesNotInTeam: RelationOneToMany<Team, UserProfile>;
-    profilesWithoutTeam: Set<any>;
+    profilesWithoutTeam: Set<string>;
     profilesInChannel: RelationOneToMany<Channel, UserProfile>;
     profilesNotInChannel: RelationOneToMany<Channel, UserProfile>;
     statuses: RelationOneToOne<UserProfile, string>;
@@ -63,3 +63,11 @@ export type UserActivity = {
         } | Array<$ID<UserProfile>>;
     };
 };
+
+export type UserStatus = {
+	user_id: string;
+	status: string;
+	manual: boolean;
+	last_activity_at: number;
+	active_channel?: string;
+}
\ No newline at end of file
diff --git a/src/types/utilities.ts b/src/types/utilities.ts
index 2c0bf357c..99cc1abd4 100644
--- a/src/types/utilities.ts
+++ b/src/types/utilities.ts
@@ -1,27 +1,27 @@
 // Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
 // See LICENSE.txt for license information.
-export type $ID<E extends {id}> = E['id'];
-export type $UserID<E extends {user_id}> = E['user_id'];
-export type $Name<E extends {name}> = E['name'];
-export type $Username<E extends {username}> = E['username'];
-export type $Email<E extends {email}> = E['email'];
-export type RelationOneToOne<E extends {id}, T> = {
+export type $ID<E extends {id: string}> = E['id'];
+export type $UserID<E extends {user_id: string}> = E['user_id'];
+export type $Name<E extends {name: string}> = E['name'];
+export type $Username<E extends {username: string}> = E['username'];
+export type $Email<E extends {email: string}> = E['email'];
+export type RelationOneToOne<E extends {id: string}, T> = {
     [x in $ID<E>]: T;
 };
-export type RelationOneToMany<E1 extends {id}, E2 extends {id}> = {
+export type RelationOneToMany<E1 extends {id: string}, E2 extends {id: string}> = {
     [x in $ID<E1>]: Array<$ID<E2>>;
 };
-export type IDMappedObjects<E extends {id}> = RelationOneToOne<E, E>;
-export type UserIDMappedObjects<E extends {user_id}> = {
+export type IDMappedObjects<E extends {id: string}> = RelationOneToOne<E, E>;
+export type UserIDMappedObjects<E extends {user_id: string}> = {
     [x in $UserID<E>]: E;
 };
-export type NameMappedObjects<E extends {name}> = {
+export type NameMappedObjects<E extends {name: string}> = {
     [x in $Name<E>]: E;
 };
-export type UsernameMappedObjects<E extends {username}> = {
+export type UsernameMappedObjects<E extends {username: string}> = {
     [x in $Username<E>]: E;
 };
-export type EmailMappedObjects<E extends {email}> = {
+export type EmailMappedObjects<E extends {email: string}> = {
     [x in $Email<E>]: E;
 };
 
diff --git a/src/utils/channel_utils.ts b/src/utils/channel_utils.ts
index 11f5e1721..e65fddc49 100644
--- a/src/utils/channel_utils.ts
+++ b/src/utils/channel_utils.ts
@@ -396,7 +396,7 @@ export function getGroupDisplayNameFromUserIds(userIds: Array<string>, profiles:
         }
     });
 
-    function sortUsernames(a, b) {
+    function sortUsernames(a: string, b: string) {
         const locale = getUserLocale(currentUserId, profiles);
         return a.localeCompare(b, locale, {numeric: true});
     }
@@ -456,7 +456,7 @@ function createMissingDirectChannels(currentUserId: string, allChannels: Array<C
         map(createFakeChannelCurried(currentUserId));
 }
 
-function completeDirectGroupInfo(usersState, teammateNameDisplay, channel) {
+function completeDirectGroupInfo(usersState: UsersState, teammateNameDisplay: string, channel: Channel) {
     const {currentUserId, profiles, profilesInChannel} = usersState;
     const profilesIds = profilesInChannel[channel.id];
     const gm = {...channel};
@@ -483,11 +483,11 @@ function completeDirectGroupInfo(usersState, teammateNameDisplay, channel) {
     return channel;
 }
 
-function isDirectChannelForUser(userId, otherUserId, channel) {
+function isDirectChannelForUser(userId: string, otherUserId: string, channel: Channel) {
     return channel.type === General.DM_CHANNEL && getUserIdFromChannelName(userId, channel.name) === otherUserId;
 }
 
-function channelHasMentions(members, channel) {
+function channelHasMentions(members: RelationOneToOne<Channel, ChannelMembership>, channel: Channel) {
     const member = members[channel.id];
     if (member) {
         return member.mention_count > 0;
@@ -637,17 +637,17 @@ function buildDirectAndGroupChannels(channels: Array<Channel>, memberships: Rela
     });
 }
 
-function buildChannelsWithMentions(channels, members, locale) {
+function buildChannelsWithMentions(channels: Array<Channel>, members: RelationOneToOne<Channel, ChannelMembership>, locale: string) {
     return channels.filter(channelHasMentions.bind(null, members)).
         sort(sortChannelsByDisplayName.bind(null, locale));
 }
 
-function buildUnreadChannels(channels, members, locale) {
+function buildUnreadChannels(channels: Array<Channel>, members: RelationOneToOne<Channel, ChannelMembership>, locale: string) {
     return channels.filter(channelHasUnreadMessages.bind(null, members)).
         sort(sortChannelsByDisplayName.bind(null, locale));
 }
 
-function getUserLocale(userId, profiles) {
+function getUserLocale(userId: string, profiles: IDMappedObjects<UserProfile>) {
     let locale = General.DEFAULT_LOCALE;
     if (profiles && profiles[userId] && profiles[userId].locale) {
         locale = profiles[userId].locale;
diff --git a/src/utils/file_utils.ts b/src/utils/file_utils.ts
index ba74131b5..2dec8f754 100644
--- a/src/utils/file_utils.ts
+++ b/src/utils/file_utils.ts
@@ -2,8 +2,11 @@
 // See LICENSE.txt for license information.
 import {Files, General} from '../constants';
 import {Client4} from 'client';
-import mimeDB from 'mime-db';
 import {FileInfo} from 'types/files';
+import {Dictionary} from 'types/utilities';
+
+const mimeDB = require('mime-db');
+
 export function getFormattedFileSize(file: FileInfo): string {
     const bytes = file.size;
     const fileSizes = [
@@ -48,13 +51,13 @@ export function getFileType(file: FileInfo): string {
     }) || 'other';
 }
 
-let extToMime;
+let extToMime: Dictionary<string>;
 function buildExtToMime() {
     extToMime = {};
     Object.keys(mimeDB).forEach((key) => {
         const mime = mimeDB[key];
         if (mime.extensions) {
-            mime.extensions.forEach((ext) => {
+            mime.extensions.forEach((ext: string) => {
                 extToMime[ext] = key;
             });
         }
diff --git a/src/utils/gfycat_sdk.ts b/src/utils/gfycat_sdk.ts
index 64e9ff7a2..fe3ce2433 100644
--- a/src/utils/gfycat_sdk.ts
+++ b/src/utils/gfycat_sdk.ts
@@ -4,9 +4,10 @@ import Gfycat from 'gfycat-sdk';
 const defaultKey = '2_KtH_W5';
 const defaultSecret = '3wLVZPiswc3DnaiaFoLkDvB4X0IV6CpMkj4tf2inJRsBY6-FnkT08zGmppWFgeof';
 let activeKey: string|null = null;
-let activeSecret: string|null = null;
-let instance: Gfycat|null = null;
-export default function(key: string, secret: string): Gfycat {
+let activeSecret: string | null = null;
+
+let instance: any = null;
+export default function(key: string, secret: string): any {
     if (instance && activeKey === key && activeSecret === secret) {
         return instance;
     }
diff --git a/src/utils/helpers.ts b/src/utils/helpers.ts
index 6c83bea71..61772a712 100644
--- a/src/utils/helpers.ts
+++ b/src/utils/helpers.ts
@@ -2,11 +2,12 @@
 // See LICENSE.txt for license information.
 import * as reselect from 'reselect';
 import shallowEqual from 'shallow-equals';
+import {Dictionary} from 'types/utilities';
 export function memoizeResult<F extends Function>(func: F): any {
     let lastArgs: IArguments|null = null;
-    let lastResult = null; // we reference arguments instead of spreading them for performance reasons
+    let lastResult: any = null; // we reference arguments instead of spreading them for performance reasons
 
-    return function shallowCompare(...args) {
+    return function shallowCompare(...args: any[]) {
         if (!shallowEqual(lastArgs, args)) {
             //eslint-disable-line prefer-rest-params
             // apply arguments instead of spreading for performance.
@@ -26,7 +27,7 @@ export function memoizeResult<F extends Function>(func: F): any {
 export const createIdsSelector = reselect.createSelectorCreator(memoizeResult);
 
 // Use this selector when you want a shallow comparison of the arguments and you don't need to memoize the result
-export const createShallowSelector = reselect.createSelectorCreator(reselect.defaultMemoize, shallowEqual);
+export const createShallowSelector = reselect.createSelectorCreator(reselect.defaultMemoize, shallowEqual as any);
 
 // isMinimumServerVersion will return true if currentVersion is equal to higher or than the
 // the provided minimum version. A non-equal major version will ignore minor and dot
@@ -101,7 +102,7 @@ export function isEmail(email: string): boolean {
     return (/^[^ ,@]+@[^ ,@]+$/).test(email);
 }
 
-export function buildQueryString(parameters: {}): string {
+export function buildQueryString(parameters: Dictionary<any>): string {
     const keys = Object.keys(parameters);
     if (keys.length === 0) {
         return '';
diff --git a/src/utils/team_utils.ts b/src/utils/team_utils.ts
index f3b031584..cde1fcc42 100644
--- a/src/utils/team_utils.ts
+++ b/src/utils/team_utils.ts
@@ -1,10 +1,11 @@
 // Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
 // See LICENSE.txt for license information.
 import {Team} from 'types/teams';
-import {IDMappedObjects} from 'types/utilities';
+import {IDMappedObjects, Dictionary} from 'types/utilities';
 import {General} from '../constants';
+
 export function teamListToMap(teamList: Array<Team>): IDMappedObjects<Team> {
-    const teams = {};
+    const teams: Dictionary<Team> = {};
     for (let i = 0; i < teamList.length; i++) {
         teams[teamList[i].id] = teamList[i];
     }
diff --git a/src/utils/theme_utils.ts b/src/utils/theme_utils.ts
index 4d84f5171..0b0255e1e 100644
--- a/src/utils/theme_utils.ts
+++ b/src/utils/theme_utils.ts
@@ -1,8 +1,9 @@
 // Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
 // See LICENSE.txt for license information.
+
 export function makeStyleFromTheme(getStyleFromTheme: (a: any) => any): (a: any) => any {
-    let lastTheme;
-    let style;
+    let lastTheme: any;
+    let style: any;
     return (theme: any) => {
         if (!style || theme !== lastTheme) {
             style = getStyleFromTheme(theme);
diff --git a/src/utils/user_utils.ts b/src/utils/user_utils.ts
index df8bafa1d..d461ffe4e 100644
--- a/src/utils/user_utils.ts
+++ b/src/utils/user_utils.ts
@@ -3,7 +3,7 @@
 import {General, Preferences} from '../constants';
 import {localizeMessage} from 'utils/i18n_utils';
 import {UserProfile} from 'types/users';
-import {IDMappedObjects, $ID} from 'types/utilities';
+import {IDMappedObjects, $ID, Dictionary} from 'types/utilities';
 export function getFullName(user: UserProfile): string {
     if (user.first_name && user.last_name) {
         return user.first_name + ' ' + user.last_name;
@@ -74,7 +74,7 @@ export function hasPostAllPublicRole(roles: string): boolean {
 }
 
 export function profileListToMap(profileList: Array<UserProfile>): IDMappedObjects<UserProfile> {
-    const profiles = {};
+    const profiles: Dictionary<UserProfile> = {};
     for (let i = 0; i < profileList.length; i++) {
         profiles[profileList[i].id] = profileList[i];
     }
diff --git a/test/test_helper.js b/test/test_helper.js
index e0fb042f6..52896e837 100644
--- a/test/test_helper.js
+++ b/test/test_helper.js
@@ -120,7 +120,7 @@ class TestHelper {
 
     fakeOutgoingHook = (teamId) => {
         return {
-            teamId,
+            team_id: teamId,
         };
     };
 
diff --git a/tsconfig.json b/tsconfig.json
index 400c2ea5a..1b1ccd915 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -1,13 +1,21 @@
 {
-    "include": ["src"],
-    "exclude": ["node_modules", "build"],
+    "include": [
+        "src"
+    ],
+    "exclude": [
+        "node_modules",
+        "build"
+    ],
     "typeAcquisition": {
         "enable": true
     },
     "compilerOptions": {
         "target": "es5",
         "module": "commonjs",
-        "lib": ["dom", "esnext"],
+        "lib": [
+            "dom",
+            "esnext"
+        ],
         "allowJs": false,
         "importHelpers": true,
         "declaration": true,
@@ -16,7 +24,7 @@
         "outDir": "./",
         "strict": false,
         "noEmit": false,
-        "noImplicitAny": false,
+        "noImplicitAny": true,
         "strictNullChecks": true,
         "strictFunctionTypes": false,
         "strictPropertyInitialization": true,
@@ -30,24 +38,47 @@
         "moduleResolution": "node",
         "baseUrl": "./",
         "paths": {
-            "utils/*": ["src/utils/*"],
-            "types/*": ["src/types/*"],
-            "constants/*": ["src/constants/*"],
-            "client": ["src/client"],
-            "selectors/*": ["src/selectors/*"],
-            "store/*": ["src/store/*"],
-            "action_types": ["src/action_types"],
-            "actions/*": ["src/action_types/*"],
-            "test/*": ["test/*"],
-            "*": ["src/*","node_modules/*"]
+            "utils/*": [
+                "src/utils/*"
+            ],
+            "types/*": [
+                "src/types/*"
+            ],
+            "constants/*": [
+                "src/constants/*"
+            ],
+            "client": [
+                "src/client"
+            ],
+            "selectors/*": [
+                "src/selectors/*"
+            ],
+            "store/*": [
+                "src/store/*"
+            ],
+            "action_types": [
+                "src/action_types"
+            ],
+            "actions/*": [
+                "src/action_types/*"
+            ],
+            "test/*": [
+                "test/*"
+            ],
+            "*": [
+                "src/*",
+                "node_modules/*"
+            ]
         },
         "plugins": [
             {
                 "transform": "@zerollup/ts-transform-paths",
-                "exclude": ["*"]
+                "exclude": [
+                    "*"
+                ]
             }
         ],
         "jsx": "react",
         "esModuleInterop": true
     }
-}
+}
\ No newline at end of file