diff --git a/lib/buffer.js b/lib/buffer.js
index d5fde6debc2f74..7c0bbbc81c6398 100644
--- a/lib/buffer.js
+++ b/lib/buffer.js
@@ -1256,6 +1256,8 @@ const kForgivingBase64AllowedChars = [
   0x2F, // /
   0x3D, // =
 ];
+const kEqualSignIndex = ArrayPrototypeIndexOf(kForgivingBase64AllowedChars,
+                                              0x3D);
 
 function atob(input) {
   // The implementation here has not been performance optimized in any way and
@@ -1267,6 +1269,7 @@ function atob(input) {
 
   input = `${input}`;
   let nonAsciiWhitespaceCharCount = 0;
+  let equalCharCount = 0;
 
   for (let n = 0; n < input.length; n++) {
     const index = ArrayPrototypeIndexOf(
@@ -1277,13 +1280,36 @@ function atob(input) {
       // The first 5 elements of `kForgivingBase64AllowedChars` are
       // ASCII whitespace char codes.
       nonAsciiWhitespaceCharCount++;
+
+      if (index === kEqualSignIndex) {
+        equalCharCount++;
+      } else if (equalCharCount) {
+        // The `=` char is only allowed at the end.
+        throw lazyDOMException('Invalid character', 'InvalidCharacterError');
+      }
+
+      if (equalCharCount > 2) {
+        // Only one more `=` is permitted after the first equal sign.
+        throw lazyDOMException('Invalid character', 'InvalidCharacterError');
+      }
     } else if (index === -1) {
       throw lazyDOMException('Invalid character', 'InvalidCharacterError');
     }
   }
 
+  let reminder = nonAsciiWhitespaceCharCount % 4;
+
+  // See #2, #3, #4 - https://infra.spec.whatwg.org/#forgiving-base64
+  if (!reminder) {
+    // Remove all trailing `=` characters and get the new reminder.
+    reminder = (nonAsciiWhitespaceCharCount - equalCharCount) % 4;
+  } else if (equalCharCount) {
+    // `=` should not in the input if there's a reminder.
+    throw lazyDOMException('Invalid character', 'InvalidCharacterError');
+  }
+
   // See #3 - https://infra.spec.whatwg.org/#forgiving-base64
-  if (nonAsciiWhitespaceCharCount % 4 === 1) {
+  if (reminder === 1) {
     throw lazyDOMException(
       'The string to be decoded is not correctly encoded.',
       'InvalidCharacterError');
@@ -1298,6 +1324,7 @@ module.exports = {
   Buffer,
   SlowBuffer,
   transcode,
+
   // Legacy
   kMaxLength,
   kStringMaxLength,
diff --git a/test/fixtures/wpt/LICENSE.md b/test/fixtures/wpt/LICENSE.md
index 39c46d03ac2988..ad4858c8745cfa 100644
--- a/test/fixtures/wpt/LICENSE.md
+++ b/test/fixtures/wpt/LICENSE.md
@@ -1,6 +1,6 @@
 # The 3-Clause BSD License
 
-Copyright © web-platform-tests contributors
+Copyright 2019 web-platform-tests contributors
 
 Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:
 
diff --git a/test/fixtures/wpt/README.md b/test/fixtures/wpt/README.md
index 63175ead2a9c2d..a4ab2175fc65a2 100644
--- a/test/fixtures/wpt/README.md
+++ b/test/fixtures/wpt/README.md
@@ -15,6 +15,7 @@ Last update:
 - dom/abort: https://github.com/web-platform-tests/wpt/tree/c49cafb491/dom/abort
 - dom/events: https://github.com/web-platform-tests/wpt/tree/f8821adb28/dom/events
 - encoding: https://github.com/web-platform-tests/wpt/tree/c1b24fce6e/encoding
+- fetch/data-urls/resources: https://github.com/web-platform-tests/wpt/tree/7c79d998ff/fetch/data-urls/resources
 - FileAPI: https://github.com/web-platform-tests/wpt/tree/3b279420d4/FileAPI
 - hr-time: https://github.com/web-platform-tests/wpt/tree/34cafd797e/hr-time
 - html/webappapis/atob: https://github.com/web-platform-tests/wpt/tree/f267e1dca6/html/webappapis/atob
diff --git a/test/fixtures/wpt/fetch/data-urls/resources/base64.json b/test/fixtures/wpt/fetch/data-urls/resources/base64.json
new file mode 100644
index 00000000000000..01f981a6502aec
--- /dev/null
+++ b/test/fixtures/wpt/fetch/data-urls/resources/base64.json
@@ -0,0 +1,82 @@
+[
+  ["", []],
+  ["abcd", [105, 183, 29]],
+  [" abcd", [105, 183, 29]],
+  ["abcd ", [105, 183, 29]],
+  [" abcd===", null],
+  ["abcd=== ", null],
+  ["abcd ===", null],
+  ["a", null],
+  ["ab", [105]],
+  ["abc", [105, 183]],
+  ["abcde", null],
+  ["𐀀", null],
+  ["=", null],
+  ["==", null],
+  ["===", null],
+  ["====", null],
+  ["=====", null],
+  ["a=", null],
+  ["a==", null],
+  ["a===", null],
+  ["a====", null],
+  ["a=====", null],
+  ["ab=", null],
+  ["ab==", [105]],
+  ["ab===", null],
+  ["ab====", null],
+  ["ab=====", null],
+  ["abc=", [105, 183]],
+  ["abc==", null],
+  ["abc===", null],
+  ["abc====", null],
+  ["abc=====", null],
+  ["abcd=", null],
+  ["abcd==", null],
+  ["abcd===", null],
+  ["abcd====", null],
+  ["abcd=====", null],
+  ["abcde=", null],
+  ["abcde==", null],
+  ["abcde===", null],
+  ["abcde====", null],
+  ["abcde=====", null],
+  ["=a", null],
+  ["=a=", null],
+  ["a=b", null],
+  ["a=b=", null],
+  ["ab=c", null],
+  ["ab=c=", null],
+  ["abc=d", null],
+  ["abc=d=", null],
+  ["ab\u000Bcd", null],
+  ["ab\u3000cd", null],
+  ["ab\u3001cd", null],
+  ["ab\tcd", [105, 183, 29]],
+  ["ab\ncd", [105, 183, 29]],
+  ["ab\fcd", [105, 183, 29]],
+  ["ab\rcd", [105, 183, 29]],
+  ["ab cd", [105, 183, 29]],
+  ["ab\u00a0cd", null],
+  ["ab\t\n\f\r cd", [105, 183, 29]],
+  [" \t\n\f\r ab\t\n\f\r cd\t\n\f\r ", [105, 183, 29]],
+  ["ab\t\n\f\r =\t\n\f\r =\t\n\f\r ", [105]],
+  ["A", null],
+  ["/A", [252]],
+  ["//A", [255, 240]],
+  ["///A", [255, 255, 192]],
+  ["////A", null],
+  ["/", null],
+  ["A/", [3]],
+  ["AA/", [0, 15]],
+  ["AAAA/", null],
+  ["AAA/", [0, 0, 63]],
+  ["\u0000nonsense", null],
+  ["abcd\u0000nonsense", null],
+  ["YQ", [97]],
+  ["YR", [97]],
+  ["~~", null],
+  ["..", null],
+  ["--", null],
+  ["__", null]
+]
diff --git a/test/fixtures/wpt/fetch/data-urls/resources/data-urls.json b/test/fixtures/wpt/fetch/data-urls/resources/data-urls.json
new file mode 100644
index 00000000000000..f318d1f3e547d3
--- /dev/null
+++ b/test/fixtures/wpt/fetch/data-urls/resources/data-urls.json
@@ -0,0 +1,214 @@
+[
+  ["data://test/,X",
+   "text/plain;charset=US-ASCII",
+   [88]],
+  ["data://test:test/,X",
+   null],
+  ["data:,X",
+   "text/plain;charset=US-ASCII",
+   [88]],
+  ["data:",
+   null],
+  ["data:text/html",
+   null],
+  ["data:text/html    ;charset=x   ",
+   null],
+  ["data:,",
+   "text/plain;charset=US-ASCII",
+   []],
+  ["data:,X#X",
+   "text/plain;charset=US-ASCII",
+   [88]],
+  ["data:,%FF",
+   "text/plain;charset=US-ASCII",
+   [255]],
+  ["data:text/plain,X",
+   "text/plain",
+   [88]],
+  ["data:text/plain ,X",
+   "text/plain",
+   [88]],
+  ["data:text/plain%20,X",
+   "text/plain%20",
+   [88]],
+  ["data:text/plain\f,X",
+   "text/plain%0c",
+   [88]],
+  ["data:text/plain%0C,X",
+   "text/plain%0c",
+   [88]],
+  ["data:text/plain;,X",
+   "text/plain",
+   [88]],
+  ["data:;x=x;charset=x,X",
+   "text/plain;x=x;charset=x",
+   [88]],
+  ["data:;x=x,X",
+   "text/plain;x=x",
+   [88]],
+  ["data:text/plain;charset=windows-1252,%C2%B1",
+   "text/plain;charset=windows-1252",
+   [194, 177]],
+  ["data:text/plain;Charset=UTF-8,%C2%B1",
+   "text/plain;charset=UTF-8",
+   [194, 177]],
+  ["data:text/plain;charset=windows-1252,áñçə💩",
+   "text/plain;charset=windows-1252",
+   [195, 161, 195, 177, 195, 167, 201, 153, 240, 159, 146, 169]],
+  ["data:text/plain;charset=UTF-8,áñçə💩",
+   "text/plain;charset=UTF-8",
+   [195, 161, 195, 177, 195, 167, 201, 153, 240, 159, 146, 169]],
+  ["data:image/gif,%C2%B1",
+   "image/gif",
+   [194, 177]],
+  ["data:IMAGE/gif,%C2%B1",
+   "image/gif",
+   [194, 177]],
+  ["data:IMAGE/gif;hi=x,%C2%B1",
+   "image/gif;hi=x",
+   [194, 177]],
+  ["data:IMAGE/gif;CHARSET=x,%C2%B1",
+   "image/gif;charset=x",
+   [194, 177]],
+  ["data: ,%FF",
+   "text/plain;charset=US-ASCII",
+   [255]],
+  ["data:%20,%FF",
+   "text/plain;charset=US-ASCII",
+   [255]],
+  ["data:\f,%FF",
+   "text/plain;charset=US-ASCII",
+   [255]],
+  ["data:%1F,%FF",
+   "text/plain;charset=US-ASCII",
+   [255]],
+  ["data:\u0000,%FF",
+   "text/plain;charset=US-ASCII",
+   [255]],
+  ["data:%00,%FF",
+   "text/plain;charset=US-ASCII",
+   [255]],
+  ["data:text/html  ,X",
+   "text/html",
+   [88]],
+  ["data:text / html,X",
+   "text/plain;charset=US-ASCII",
+   [88]],
+  ["data:†,X",
+   "text/plain;charset=US-ASCII",
+   [88]],
+  ["data:†/†,X",
+   "%e2%80%a0/%e2%80%a0",
+   [88]],
+  ["data:X,X",
+   "text/plain;charset=US-ASCII",
+   [88]],
+  ["data:image/png,X X",
+   "image/png",
+   [88, 32, 88]],
+  ["data:application/javascript,X X",
+   "application/javascript",
+   [88, 32, 88]],
+  ["data:application/xml,X X",
+   "application/xml",
+   [88, 32, 88]],
+  ["data:text/javascript,X X",
+   "text/javascript",
+   [88, 32, 88]],
+  ["data:text/plain,X X",
+   "text/plain",
+   [88, 32, 88]],
+  ["data:unknown/unknown,X X",
+   "unknown/unknown",
+   [88, 32, 88]],
+  ["data:text/plain;a=\",\",X",
+   "text/plain;a=\"\"",
+   [34, 44, 88]],
+  ["data:text/plain;a=%2C,X",
+   "text/plain;a=%2C",
+   [88]],
+  ["data:;base64;base64,WA",
+   "text/plain",
+   [88]],
+  ["data:x/x;base64;base64,WA",
+   "x/x",
+   [88]],
+  ["data:x/x;base64;charset=x,WA",
+   "x/x;charset=x",
+   [87, 65]],
+  ["data:x/x;base64;charset=x;base64,WA",
+   "x/x;charset=x",
+   [88]],
+  ["data:x/x;base64;base64x,WA",
+   "x/x",
+   [87, 65]],
+  ["data:;base64,W%20A",
+   "text/plain;charset=US-ASCII",
+   [88]],
+  ["data:;base64,W%0CA",
+   "text/plain;charset=US-ASCII",
+   [88]],
+  ["data:x;base64x,WA",
+   "text/plain;charset=US-ASCII",
+   [87, 65]],
+  ["data:x;base64;x,WA",
+   "text/plain;charset=US-ASCII",
+   [87, 65]],
+  ["data:x;base64=x,WA",
+   "text/plain;charset=US-ASCII",
+   [87, 65]],
+  ["data:; base64,WA",
+   "text/plain;charset=US-ASCII",
+   [88]],
+  ["data:;  base64,WA",
+   "text/plain;charset=US-ASCII",
+   [88]],
+  ["data:  ;charset=x   ;  base64,WA",
+   "text/plain;charset=x",
+   [88]],
+  ["data:;base64;,WA",
+   "text/plain",
+   [87, 65]],
+  ["data:;base64 ,WA",
+   "text/plain;charset=US-ASCII",
+   [88]],
+  ["data:;base64   ,WA",
+   "text/plain;charset=US-ASCII",
+   [88]],
+  ["data:;base 64,WA",
+   "text/plain",
+   [87, 65]],
+  ["data:;BASe64,WA",
+   "text/plain;charset=US-ASCII",
+   [88]],
+  ["data:;%62ase64,WA",
+   "text/plain",
+   [87, 65]],
+  ["data:%3Bbase64,WA",
+   "text/plain;charset=US-ASCII",
+   [87, 65]],
+  ["data:;charset=x,X",
+   "text/plain;charset=x",
+   [88]],
+  ["data:; charset=x,X",
+   "text/plain;charset=x",
+   [88]],
+  ["data:;charset =x,X",
+   "text/plain",
+   [88]],
+  ["data:;charset= x,X",
+   "text/plain;charset=\" x\"",
+   [88]],
+  ["data:;charset=,X",
+   "text/plain",
+   [88]],
+  ["data:;charset,X",
+   "text/plain",
+   [88]],
+  ["data:;charset=\"x\",X",
+   "text/plain;charset=x",
+   [88]],
+  ["data:;CHARSET=\"X\",X",
+   "text/plain;charset=X",
+   [88]]
+]
diff --git a/test/fixtures/wpt/versions.json b/test/fixtures/wpt/versions.json
index 3e223cd7d93b35..575090d02645ba 100644
--- a/test/fixtures/wpt/versions.json
+++ b/test/fixtures/wpt/versions.json
@@ -19,6 +19,10 @@
     "commit": "c1b24fce6e625c1b79124a58f27bf9adce02d5d7",
     "path": "encoding"
   },
+  "fetch/data-urls/resources": {
+    "commit": "7c79d998ff42e52de90290cb847d1b515b3b58f7",
+    "path": "fetch/data-urls/resources"
+  },
   "FileAPI": {
     "commit": "3b279420d40afea32506e823f9ac005448f4f3d8",
     "path": "FileAPI"
diff --git a/test/wpt/status/html/webappapis/atob.json b/test/wpt/status/html/webappapis/atob.json
index 67345db26305af..2c63c0851048d8 100644
--- a/test/wpt/status/html/webappapis/atob.json
+++ b/test/wpt/status/html/webappapis/atob.json
@@ -1,5 +1,2 @@
 {
-  "base64.any.js": {
-    "skip": "no such file or directory fetch/data-urls/resources/base64.json"
-  }
 }