html5ever is an HTML parser developed as part of the Servo project. It can parse and serialize HTML according to the WHATWG specs (aka "HTML5"). There are some omissions at present, most of which are documented in the bug tracker. html5ever passes all tokenizer tests from html5lib-tests, and most tree builder tests outside of the unimplemented features. The goal is to pass all html5lib tests, and also provide all hooks needed by a production web browser, e.g. document.write.