Define the correct environment for a Mod

Define the correct environment for a Mod

It's important to define the correct environment for a Mod to make sure a client-side mod is not crashing a server or in rare cases that a server-side mod is not crashing a client.

How to define the correct environment for a Mod?

Depending on the mod loader you are using, you have to define the correct environment for your mod.

Forge

For Forge there are two options to define the correct environment for a mod.

Dependencies inside the mods.toml file

The 'mods.toml' file is located inside the META-INF folder of the mod jar file. Its includes the dependencies and the environment for the mod.

There is normally a dependency section for forge and minecraft which allows to define the correct side for the mod.

Example:

[[mods]]
modId = "example_mod"

[[dependencies.example_mod]]
modId = "forge"
mandatory = true
versionRange = "[36.1.0,)"
ordering = "NONE"
side = "CLIENT"
[[dependencies.example_mod]]
modId = "minecraft"
mandatory = true
versionRange = "[1.16.5,)"
ordering = "NONE"
side = "CLIENT"

The side parameter can be CLIENT, SERVER or BOTH:

• CLIENT means that the mod is physically loaded on the client side.
• SERVER means that the mod is physically loaded on the server side.
• BOTH means that the mod physically loaded on the client and server side.

See: https://docs.minecraftforge.net/en/1.20.x/gettingstarted/modfiles/

Display Test

The displayTest annotation is used to show a warning message if the mod is loaded on the wrong side. This is mostly used on servers to show you a warning message before you are connecting to the server.

You can define the displayTest inside the mods.toml file like:

[[mods]]
modId = "example_mod"
displayName = "Example Mod"
displayURL = "https://www.example.com"
displayAuthors = "Markus Bordihn"
displayDescription = "This is an example mod."
displayTest = "MATCH_VERSION"

The displayTest parameter can be MATCH_VERSION, IGNORE_SERVER_VERSION, IGNORE_ALL_VERSION or NONE:

• MATCH_VERSION Use this option if your mod involves both server and client elements. A red X will appear if the versions on the client and server differ. This is the default behavior for mods with server and client components.
• IGNORE_SERVER_VERSION Ideal for server-only mods. Your mod won't trigger a red X if it's present on the server but not on the client. Recommended for mods that exclusively function on the server side.
• IGNORE_ALL_VERSION A special case for mods with no server component like pure client-side mods. Won't cause a red X whether present on the client or the server. Use this option only if your mod lacks a server component.
• NONE No display test is set by default. You must define your own display test using IExtensionPoint.DisplayTest inside your mod's code. This option allows you to create a custom scheme based on your mod's requirements.

See: https://docs.minecraftforge.net/en/1.20.x/concepts/sides/#writing-one-sided-mods

Fabric

For Fabric there is only one option to define the correct environment for a mod inside the fabric.mod.json file.

Example:

{
  "schemaVersion": 1,
  "id": "example_mod",
  "version": "1.0.0",
  "name": "Example Mod",
  "description": "This is an example mod.",
  "authors": [
    "Markus Bordihn"
  ],
  "contact": {
    "homepage": "https://www.example.com"
  },
  "license": "MIT",
  "icon": "assets/example_mod/icon.png",
  "environment": "client"
}

The environment parameter can be client, server or *:

• * Runs everywhere. Default for client and server mods.
• client Runs on the client side for client side mods.
• server Runs on the server side for server side mods.

See: https://fabricmc.net/wiki/documentation:fabric_mod_json_spec

Quilt

For Quilt the mod environment is defined inside the quilt.mod.json file in the minecraft section.

Example:

{
  "schema_version": 1,
  "quilt_loader": {
    "group": "org.quiltmc",
    "id": "example_mod",
    "metadata": {
      "name": "Quilt Example Mod",
      "description": "An example mod for the Quilt ecosystem."
    }
  },
  "minecraft": {
    "environment": "client"
  }
}

The environment parameter can be client, dedicated_server or *:

• * Runs everywhere. Default for client and server mods.
• client Runs on the client side for client side mods.
• dedicated_server Runs on the server side for server side mods.

See: https://github.com/QuiltMC/rfcs/blob/main/specification/0002-quilt.mod.json.md#the-minecraft-field