diff --git a/README.md b/README.md
index ca57dce..7eccad4 100644
--- a/README.md
+++ b/README.md
@@ -1,5 +1,5 @@
 # nuid
-![nuid](https://github.com/nomasystems/nuid/actions/workflows/build.yml/badge.svg)
+[![nuid](https://github.com/nomasystems/nuid/actions/workflows/ci.yml/badge.svg)](https://github.com/nomasystems/nuid/actions/workflows/ci.yml)
 
 `nuid` is an OTP library to generate unique identifiers.
 
diff --git a/rebar.config b/rebar.config
index 0d81dc4..2d23bce 100644
--- a/rebar.config
+++ b/rebar.config
@@ -49,6 +49,7 @@
 ]}.
 
 {cover_opts, [verbose]}.
+{cover_excl_mods, [nuid_base64]}.
 {cover_enabled, true}.
 
 {xref_ignores, [nuid]}.
diff --git a/src/nuid_base64.erl b/src/nuid_base64.erl
index 97f1911..8b60d96 100644
--- a/src/nuid_base64.erl
+++ b/src/nuid_base64.erl
@@ -1,7 +1,7 @@
 %%
 %% %CopyrightBegin%
 %%
-%% Copyright Ericsson AB 2007-2021. All Rights Reserved.
+%% Copyright Ericsson AB 2007-2023. All Rights Reserved.
 %%
 %% Licensed under the Apache License, Version 2.0 (the "License");
 %% you may not use this file except in compliance with the License.
@@ -21,68 +21,109 @@
 
 -module(nuid_base64).
 
--export([encode/1, decode/1]).
+-export([
+    encode/1,
+    decode/1
+]).
 
-%% RFC 4648§5: base64url - Base 64 Encoding alphabet
-%-type base64_alphabet() :: $0..$9 | $- | $A..$Z | $_ | $a..$z.
-%% Alphabet reordered to be lexicographically ordered.
+%% RFC 4648: Base 64 Encoding alphabet
+%% -type base64_alphabet() :: $A..$Z | $a..$z | $0..$9 | $- | $_.
+%% Section 4, `urlsafe'  for RFC 4648 Section 5.
+%% It's been reordered to be lexicographically sortable.
 
 %% The following type is a subtype of string() for return values
 %% of encoding functions.
 -type base64_binary() :: binary().
 
+%% Decoded sequence of octets
+-type byte_string() :: [byte()].
+
 -spec encode(Data) -> Base64 when
-    Data :: binary(),
+    Data :: byte_string() | binary(),
     Base64 :: base64_binary().
 
-encode(Bin) ->
+encode(Bin) when is_binary(Bin) ->
     encode_binary(Bin, <<>>).
 
+encode_binary(<<B1:6, B2:6, B3:6, B4:6, B5:6, B6:6, B7:6, B8:6, Ls/bits>>, A) ->
+    encode_binary(
+        Ls,
+        <<A/bits, (b64e(B1)):8, (b64e(B2)):8, (b64e(B3)):8, (b64e(B4)):8, (b64e(B5)):8,
+            (b64e(B6)):8, (b64e(B7)):8, (b64e(B8)):8>>
+    );
 encode_binary(<<>>, A) ->
     A;
-encode_binary(<<B1:8>>, A) ->
-    <<A/bits, (b64e(B1 bsr 2)):8, (b64e((B1 band 3) bsl 4)):8>>;
-encode_binary(<<B1:8, B2:8>>, A) ->
-    <<A/bits, (b64e(B1 bsr 2)):8, (b64e(((B1 band 3) bsl 4) bor (B2 bsr 4))):8,
-        (b64e((B2 band 15) bsl 2)):8>>;
-encode_binary(<<B1:8, B2:8, B3:8, Ls/bits>>, A) ->
-    BB = (B1 bsl 16) bor (B2 bsl 8) bor B3,
+encode_binary(<<B1:6, B2:6, B3:6, B4:6, Ls/bits>>, A) ->
     encode_binary(
         Ls,
-        <<A/bits, (b64e(BB bsr 18)):8, (b64e((BB bsr 12) band 63)):8, (b64e((BB bsr 6) band 63)):8,
-            (b64e(BB band 63)):8>>
-    ).
+        <<A/bits, (b64e(B1)):8, (b64e(B2)):8, (b64e(B3)):8, (b64e(B4)):8>>
+    );
+encode_binary(<<B1:6, B2:2>>, A) ->
+    E1 = b64e(B1),
+    E2 = b64e(B2 bsl 4),
+    <<A/bits, E1, E2, $=, $=>>;
+encode_binary(<<B1:6, B2:6, B3:4>>, A) ->
+    E1 = b64e(B1),
+    E2 = b64e(B2),
+    E3 = b64e(B3 bsl 2),
+    <<A/bits, E1, E2, E3, $=>>.
 
 %% mime_decode strips away all characters not Base64 before
 %% converting, whereas decode crashes if an illegal character is found
+
 -spec decode(Base64) -> Data when
     Base64 :: base64_binary(),
     Data :: binary().
 
-decode(Bin) ->
-    decode_binary(Bin, <<>>).
-
-decode_binary(<<C1:8, Cs/bits>>, A) ->
-    decode_binary(Cs, A, b64d(C1));
+decode(Base64) when is_binary(Base64) ->
+    decode_binary(Base64, <<>>).
+
+decode_binary(<<C1:8, C2:8, C3:8, C4:8, Cs/bits>>, A) ->
+    case {b64d(C1), b64d(C2), b64d(C3), b64d(C4)} of
+        {B1, B2, B3, B4} when
+            is_integer(B1),
+            is_integer(B2),
+            is_integer(B3),
+            is_integer(B4)
+        ->
+            decode_binary(Cs, <<A/bits, B1:6, B2:6, B3:6, B4:6>>);
+        {B1, B2, B3, B4} ->
+            dec_bin(Cs, B1, B2, B3, B4, A)
+    end;
 decode_binary(<<>>, A) ->
-    A.
+    A;
+decode_binary(<<C1:8, Cs/bits>>, A) ->
+    B1 = b64d(C1),
+    decode_binary(Cs, A, B1).
+
+dec_bin(Cs, B1, B2, B3, B4, A) ->
+    decode_binary(Cs, <<A/bits, B1:6, B2:6, B3:6, B4:6>>).
 
 decode_binary(<<C2:8, Cs/bits>>, A, B1) ->
-    decode_binary(Cs, A, B1, b64d(C2)).
+    B2 = b64d(C2),
+    decode_binary(Cs, A, B1, B2).
 
 decode_binary(<<C3:8, Cs/bits>>, A, B1, B2) ->
-    decode_binary(Cs, A, B1, B2, b64d(C3));
-decode_binary(<<>>, A, B1, B2) ->
-    <<A/bits, B1:6, (B2 bsr 4):2>>.
+    B3 = b64d(C3),
+    decode_binary(Cs, A, B1, B2, B3);
+decode_binary(<<_Cs/bits>>, _A, _B1, _B2) ->
+    missing_padding_error().
 
 decode_binary(<<C4:8, Cs/bits>>, A, B1, B2, B3) ->
     B4 = b64d(C4),
     decode_binary(Cs, <<A/bits, B1:6, B2:6, B3:6, B4:6>>);
-decode_binary(<<>>, A, B1, B2, B3) ->
-    <<A/bits, B1:6, B2:6, (B3 bsr 2):4>>.
+decode_binary(<<>>, _A, _B1, _B2, _B3) ->
+    missing_padding_error().
 
 %%%========================================================================
-%%% Internal functions
+%%% Error handling functions
+%%%========================================================================
+
+% always inlined for useful stacktraces when called in tail position
+-compile({inline, missing_padding_error/0}).
+missing_padding_error() ->
+    error(missing_padding, none, [{error_info, #{}}]).
+
 %%%========================================================================
 
 %% accessors
@@ -178,36 +219,3 @@ b64e(X) ->
             $z
         }
     ).
-
-%%-----------------------------------------------------------------------
-%% Code to generate decode table
-%%-----------------------------------------------------------------------
-%% code({value, {Pos, _Value}}) ->
-%%     Pos;
-%% code(_) ->
-%%     bad.
-%% 
-%% alphabet_pos([], _Pos, Acc) ->
-%%     lists:reverse(Acc);
-%% alphabet_pos([Char | Rest], Pos, Acc) ->
-%%     alphabet_pos(Rest, Pos + 1, [{Pos, Char} | Acc]).
-%% 
-%% decode_tuple(AlphabetPos) ->
-%%     Seq = lists:seq(1, 256),
-%%     decode_tuple(AlphabetPos, Seq, []).
-%% 
-%% 
-%% decode_tuple(_AlphabetPos, [], Acc) ->
-%%     list_to_tuple(lists:reverse(Acc));
-%% decode_tuple(AlphabetPos, [Char | Rest], Acc) ->
-%%     Value = code(lists:keysearch(Char, 2, AlphabetPos)),
-%%     decode_tuple(AlphabetPos, Rest, [Value | Acc]).
-%% 
-%% decode_table() ->
-%%     Alphabet = [$-, $0, $1, $2, $3, $4, $5, $6, $7, $8, $9,
-%%          $A, $B, $C, $D, $E, $F, $G, $H, $I, $J, $K, $L, $M, $N,
-%%          $O, $P, $Q, $R, $S, $T, $U, $V, $W, $X, $Y, $Z,
-%%          $_, $a, $b, $c, $d, $e, $f, $g, $h, $i, $j, $k, $l, $m, $n,
-%%          $o, $p, $q, $r, $s, $t, $u, $v, $w, $x, $y, $z],
-%%     AlphabetPos = alphabet_pos(Alphabet, 0, []),
-%%     decode_tuple(AlphabetPos).