Polyfill for the Encoding Living Standard's API
JavaScript HTML
Latest commit b98ab30 Jan 6, 2017 @inexorabletash 0.6.4



This is a polyfill for the Encoding Living Standard API for the Web, allowing encoding and decoding of textual data to and from Typed Array buffers for binary data in JavaScript.

By default it adheres to the spec and does not support encoding to legacy encodings, only decoding. It is also implemented to match the specification's algorithms, rather than for performance. The intended use is within Web pages, so it has no dependency on server frameworks or particular module schemes.

Basic examples and tests are included.


There are a few ways you can get the text-encoding library.


text-encoding is on npm. Simply run:

npm install text-encoding

Or add it to your package.json dependencies.


text-encoding is on bower as well. Install with bower like so:

bower install text-encoding

Or add it to your bower.json dependencies.

HTML Page Usage

  <!-- Required for non-UTF encodings -->
  <script src="encoding-indexes.js"></script>
  <script src="encoding.js"></script>

API Overview

Basic Usage

  var uint8array = new TextEncoder().encode(string);
  var string = new TextDecoder(encoding).decode(uint8array);

Streaming Decode

  var string = "", decoder = new TextDecoder(encoding), buffer;
  while (buffer = next_chunk()) {
    string += decoder.decode(buffer, {stream:true});
  string += decoder.decode(); // finish the stream


All encodings from the Encoding specification are supported:

utf-8 ibm866 iso-8859-2 iso-8859-3 iso-8859-4 iso-8859-5 iso-8859-6 iso-8859-7 iso-8859-8 iso-8859-8-i iso-8859-10 iso-8859-13 iso-8859-14 iso-8859-15 iso-8859-16 koi8-r koi8-u macintosh windows-874 windows-1250 windows-1251 windows-1252 windows-1253 windows-1254 windows-1255 windows-1256 windows-1257 windows-1258 x-mac-cyrillic gb18030 hz-gb-2312 big5 euc-jp iso-2022-jp shift_jis euc-kr replacement utf-16be utf-16le x-user-defined

(Some encodings may be supported under other names, e.g. ascii, iso-8859-1, etc. See Encoding for additional labels for each encoding.)

Encodings other than utf-8, utf-16le and utf-16be require an additional encoding-indexes.js file to be included. It is rather large (596kB uncompressed, 188kB gzipped); portions may be deleted if support for some encodings is not required.

Non-Standard Behavior

As required by the specification, only encoding to utf-8 is supported. If you want to try it out, you can force a non-standard behavior by passing the NONSTANDARD_allowLegacyEncoding option to TextEncoder and a label. For example:

var uint8array = new TextEncoder(
  'windows-1252', { NONSTANDARD_allowLegacyEncoding: true }).encode(text);

But note that the above won't work if you're using the polyfill in a browser that natively supports the TextEncoder API natively, since the polyfill won't be used!

You can force the polyfill to be used by using this before the polyfill:

window.TextEncoder = window.TextDecoder = null;

To support the legacy encodings (which may be stateful), the TextEncoder encode() method accepts an optional dictionary and stream option, e.g. encoder.encode(string, {stream: true}); This is not needed for standard encoding since the input is always in complete code points.