A robust & character encoding–agnostic JavaScript implementation of the `Q` encoding as defined by RFC 2047.

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q-encoding is a character encoding–agnostic JavaScript implementation of the Q encoding as defined by RFC 2047. It can be used to encode data with any character encoding to its Q-encoded form, or the other way around (i.e. decoding).


Via npm:
npm install q-encoding

Via Bower:
bower install q-encoding

Via Component:
component install mathiasbynens/q-encoding

In a browser:
<script src="q.js"></script>

In Narwhal, Node.js, and RingoJS:
var q = require('q-encoding');

In Rhino:

Using an AMD loader like RequireJS:
    'paths': {
      'q-encoding': 'path/to/q-encoding'
  function(q) {



A string representing the semantic version number.


This function takes an encoded byte string (the input parameter) and Q-encodes it. Each item in the input string represents an octet as per the desired character encoding. Here’s an example that uses UTF-8:
var utf8 = require('utf8');

q.encode(utf8.encode('foo = bar'));
// → 'foo_=3D_bar'

// → 'I=C3=B1t=C3=ABrn=C3=A2ti=C3=B4n=C3=A0liz=C3=A6ti=C3=B8n=E2=98=83=F0=9F=92=A9'


This function takes a Q-encoded string of text (the text parameter) and Q-decodes it. The return value is a ‘byte string’, i.e. a string of which each item represents an octet as per the character encoding that’s being used. Here’s an example that uses UTF-8:
var utf8 = require('utf8');

// → 'foo = bar'

// → 'Iñtërnâtiônàlizætiøn☃💩'

Using the q binary

To use the q binary in your shell, simply install q-encoding globally using npm:
npm install -g q-encoding

After that, you’ll be able to use q on the command line. Note that while the q-encoding library itself is character encoding–agnostic, the command-line tool applies the UTF-8 character encoding on all input.
$ q --encode 'foo = bar'

$ q --decode 'foo_=3D_bar'
foo = bar

Read a local text file, Quoted-Printable-encode it, and save the result to a new file:
$ q --encode < foo.txt > foo-q.txt

Or do the same with an online text file:
$ curl -sL '' | q --encode > q.txt

Or, the opposite — read a local file containing a Quoted-Printable-encoded message, decode it back to plain text, and save the result to a new file:
$ q --decode < q.txt > original.txt

See q --help for the full list of options.


q-encoding is designed to work in at least Node.js v0.10.0, Narwhal 0.3.2, RingoJS 0.8-0.9, PhantomJS 1.9.0, Rhino 1.7RC4, as well as old and modern versions of Chrome, Firefox, Safari, Opera, and Internet Explorer.

Unit tests & code coverage

After cloning this repository, run npm install to install the dependencies needed for development and testing. You may want to install Istanbul globally using npm install istanbul -g.
Once that’s done, you can run the unit tests in Node using npm test or node tests/tests.js. To run the tests in Rhino, Ringo, Narwhal, and web browsers as well, use grunt test.
To generate the code coverage report, use grunt cover.


| twitter/mathias | |---| | Mathias Bynens |


q-encoding is available under the MIT license.