This is a fork of Aria Stewart's HTML5 parser: https://github.com/aredridel/html5 I have modified it to run in the browser instead of Node and to live in a single file. I've also decoupled it from jsdom so that it returns a simpler parse tree. Loading html5parser.js defines HTML5.parseDocument() and HTML5.parseFragment(). The parent project from which this one is forked has a lot of tests, and is presumably a pretty compliant parser, through I have not run those tests myself. I may have broken the parsing functionality while making my modifications, but it seems to work okay for me in casual testing.