html5lib ports (providing a similar public API):

  * Python
    * [html5lib-python](https://github.com/html5lib/html5lib-python): the original html5lib implementation
  * PHP
    * [html5lib-php](https://github.com/html5lib/html5lib-php): dated, unmaintained, port
  * Ruby
    * [html5lib-ruby](https://github.com/html5lib/html5lib-ruby): dated, unmaintained, port
  * Dart
    * [Dart html5lib](https://github.com/dart-lang/html5lib): a third-party port to Dart.

Other HTML parsers:

  * JavaScript
    * [HTML5 parser for node.js](https://github.com/aredridel/html5) by Aria Stewart
    * [dom.js implementation of DOM4](https://github.com/andreasgal/dom.js) by Andreas Gal and David Flanagan
    * [Live DOM Viewer](http://livedom.validator.nu/) compiled via GWT by Henri Sivonen
  * Java
    * [Validator.nu HTML parser](http://about.validator.nu/htmlparser/) by Henri Sivonen