Punycode.js Build status Dependency status

A robust Punycode converter that fully complies to RFC 3492 and RFC 5891, and works on nearly all JavaScript platforms.

This JavaScript library is the result of comparing, optimizing and documenting different open-source implementations of the Punycode algorithm:

This project is bundled with Node.js v0.6.2+.


Via npm (only required for Node.js releases older than v0.6.2):

npm install punycode

Via Bower:

bower install punycode

Via Component:

component install bestiejs/punycode.js

In a browser:

<script src="punycode.js"></script>

In Narwhal, Node.js, and RingoJS:

var punycode = require('punycode');

In Rhino:


Using an AMD loader like RequireJS:

    'paths': {
      'punycode': 'path/to/punycode'
  function(punycode) {



Converts a Punycode string of ASCII symbols to a string of Unicode symbols.

// decode domain name parts
punycode.decode('maana-pta'); // 'mañana'
punycode.decode('--dqo34k'); // '☃-⌘'


Converts a string of Unicode symbols to a Punycode string of ASCII symbols.

// encode domain name parts
punycode.encode('mañana'); // 'maana-pta'
punycode.encode('☃-⌘'); // '--dqo34k'


Converts a Punycode string representing a domain name to Unicode. Only the Punycoded parts of the domain name will be converted, i.e. it doesn’t matter if you call it on a string that has already been converted to Unicode.

// decode domain names
punycode.toUnicode('xn--maana-pta.com'); // 'mañana.com'
punycode.toUnicode('xn----dqo34k.com'); // '☃-⌘.com'


Converts a Unicode string representing a domain name to Punycode. Only the non-ASCII parts of the domain name will be converted, i.e. it doesn’t matter if you call it with a domain that's already in ASCII.

// encode domain names
punycode.toASCII('mañana.com'); // 'xn--maana-pta.com'
punycode.toASCII('☃-⌘.com'); // 'xn----dqo34k.com'



Creates an array containing the numeric code point values of each Unicode symbol in the string. While JavaScript uses UCS-2 internally, this function will convert a pair of surrogate halves (each of which UCS-2 exposes as separate characters) into a single code point, matching UTF-16.

punycode.ucs2.decode('abc'); // [0x61, 0x62, 0x63]
// surrogate pair for U+1D306 TETRAGRAM FOR CENTRE:
punycode.ucs2.decode('\uD834\uDF06'); // [0x1D306]


Creates a string based on an array of numeric code point values.

punycode.ucs2.encode([0x61, 0x62, 0x63]); // 'abc'
punycode.ucs2.encode([0x1D306]); // '\uD834\uDF06'


A string representing the current Punycode.js version number.

Full API documentation is available.

Unit tests & code coverage

After cloning this repository, run npm install --dev to install the dependencies needed for Punycode.js 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, PhantomJS, and web browsers as well, use grunt test.

To generate the code coverage report, use grunt cover.

Feel free to fork if you see possible improvements!


Mathias Bynens


John-David Dalton


Punycode.js is dual licensed under the MIT and GPL licenses.