diff --git a/lib/internal/encoding.js b/lib/internal/encoding.js
index 996b2506a49d3b..a9bfb665c2f1e8 100644
--- a/lib/internal/encoding.js
+++ b/lib/internal/encoding.js
@@ -76,8 +76,11 @@ const empty = new Uint8Array(0);
 
 const encodings = new SafeMap([
   ['unicode-1-1-utf-8', 'utf-8'],
+  ['unicode11utf8', 'utf-8'],
+  ['unicode20utf8', 'utf-8'],
   ['utf8', 'utf-8'],
   ['utf-8', 'utf-8'],
+  ['x-unicode20utf8', 'utf-8'],
   ['866', 'ibm866'],
   ['cp866', 'ibm866'],
   ['csibm866', 'ibm866'],
@@ -176,6 +179,7 @@ const encodings = new SafeMap([
   ['iso885915', 'iso-8859-15'],
   ['iso_8859-15', 'iso-8859-15'],
   ['l9', 'iso-8859-15'],
+  ['iso-8859-16', 'iso-8859-16'],
   ['cskoi8r', 'koi8-r'],
   ['koi', 'koi8-r'],
   ['koi8', 'koi8-r'],
@@ -283,9 +287,22 @@ const encodings = new SafeMap([
   ['ksc5601', 'euc-kr'],
   ['ksc_5601', 'euc-kr'],
   ['windows-949', 'euc-kr'],
+  ['csiso2022kr', 'replacement'],
+  ['hz-gb-2312', 'replacement'],
+  ['iso-2022-cn', 'replacement'],
+  ['iso-2022-cn-ext', 'replacement'],
+  ['iso-2022-kr', 'replacement'],
+  ['replacement', 'replacement'],
+  ['unicodefffe', 'utf-16be'],
   ['utf-16be', 'utf-16be'],
+  ['csunicode', 'utf-16le'],
+  ['iso-10646-ucs-2', 'utf-16le'],
+  ['ucs-2', 'utf-16le'],
+  ['unicode', 'utf-16le'],
+  ['unicodefeff', 'utf-16le'],
   ['utf-16le', 'utf-16le'],
   ['utf-16', 'utf-16le'],
+  ['x-user-defined', 'x-user-defined'],
 ]);
 
 // Unfortunately, String.prototype.trim also removes non-ascii whitespace,
diff --git a/test/parallel/test-whatwg-encoding-custom-internals.js b/test/parallel/test-whatwg-encoding-custom-internals.js
index c810b43b1ae447..505e623a681998 100644
--- a/test/parallel/test-whatwg-encoding-custom-internals.js
+++ b/test/parallel/test-whatwg-encoding-custom-internals.js
@@ -13,10 +13,20 @@ const { getEncodingFromLabel } = require('internal/encoding');
   const mappings = {
     'utf-8': [
       'unicode-1-1-utf-8',
+      'unicode11utf8',
+      'unicode20utf8',
       'utf8',
+      'x-unicode20utf8',
+    ],
+    'utf-16be': [
+      'unicodefffe',
     ],
-    'utf-16be': [],
     'utf-16le': [
+      'csunicode',
+      'iso-10646-ucs-2',
+      'ucs-2',
+      'unicode',
+      'unicodefeff',
       'utf-16',
     ],
     'ibm866': [
@@ -258,7 +268,15 @@ const { getEncodingFromLabel } = require('internal/encoding');
       'ksc5601',
       'ksc_5601',
       'windows-949',
-    ]
+    ],
+    'replacement': [
+      'csiso2022kr',
+      'hz-gb-2312',
+      'iso-2022-cn',
+      'iso-2022-cn-ext',
+      'iso-2022-kr',
+    ],
+    'x-user-defined': []
   };
   Object.entries(mappings).forEach((i) => {
     const enc = i[0];
diff --git a/test/parallel/test-whatwg-encoding-custom-textdecoder-api-invalid-label.js b/test/parallel/test-whatwg-encoding-custom-textdecoder-api-invalid-label.js
index a701d79a285a16..569c17baff4b6e 100644
--- a/test/parallel/test-whatwg-encoding-custom-textdecoder-api-invalid-label.js
+++ b/test/parallel/test-whatwg-encoding-custom-textdecoder-api-invalid-label.js
@@ -8,8 +8,17 @@ const assert = require('assert');
 [
   'utf-8',
   'unicode-1-1-utf-8',
+  'unicode11utf8',
+  'unicode20utf8',
+  'x-unicode20utf8',
   'utf8',
+  'unicodefffe',
   'utf-16be',
+  'csunicode',
+  'iso-10646-ucs-2',
+  'ucs-2',
+  'unicode',
+  'unicodefeff',
   'utf-16le',
   'utf-16',
 ].forEach((i) => {
diff --git a/test/parallel/test-whatwg-encoding-custom-textdecoder.js b/test/parallel/test-whatwg-encoding-custom-textdecoder.js
index e4379aa03f870d..835c4d962d2ada 100644
--- a/test/parallel/test-whatwg-encoding-custom-textdecoder.js
+++ b/test/parallel/test-whatwg-encoding-custom-textdecoder.js
@@ -13,19 +13,21 @@ const util = require('util');
 const buf = Buffer.from([0xef, 0xbb, 0xbf, 0x74, 0x65,
                          0x73, 0x74, 0xe2, 0x82, 0xac]);
 
+const encoding_sets = ['unicode-1-1-utf-8', 'unicode11utf8', 'unicode20utf8',
+                       'utf8', 'utf-8', 'x-unicode20utf8'];
 // Make Sure TextDecoder exist
 assert(TextDecoder);
 
 // Test TextDecoder, UTF-8, fatal: false, ignoreBOM: false
 {
-  ['unicode-1-1-utf-8', 'utf8', 'utf-8'].forEach((i) => {
+  encoding_sets.forEach((i) => {
     const dec = new TextDecoder(i);
     assert.strictEqual(dec.encoding, 'utf-8');
     const res = dec.decode(buf);
     assert.strictEqual(res, 'test€');
   });
 
-  ['unicode-1-1-utf-8', 'utf8', 'utf-8'].forEach((i) => {
+  encoding_sets.forEach((i) => {
     const dec = new TextDecoder(i);
     let res = '';
     res += dec.decode(buf.slice(0, 8), { stream: true });
@@ -36,13 +38,13 @@ assert(TextDecoder);
 
 // Test TextDecoder, UTF-8, fatal: false, ignoreBOM: true
 {
-  ['unicode-1-1-utf-8', 'utf8', 'utf-8'].forEach((i) => {
+  encoding_sets.forEach((i) => {
     const dec = new TextDecoder(i, { ignoreBOM: true });
     const res = dec.decode(buf);
     assert.strictEqual(res, '\ufefftest€');
   });
 
-  ['unicode-1-1-utf-8', 'utf8', 'utf-8'].forEach((i) => {
+  encoding_sets.forEach((i) => {
     const dec = new TextDecoder(i, { ignoreBOM: true });
     let res = '';
     res += dec.decode(buf.slice(0, 8), { stream: true });