This server hosts the syntax definitions for HTML 5, currently implemented in RelaxNG+Schematron. The original RelaxNG framework and Core modules were designed and written by fantasai. Henri Sivonen has add Web Forms 1 and 2 and HTML5 features. It is now being maintained by W3C. A web-based validation service using this schema is available. It has also been incorporated into the W3C HTML5 Validator.

Version control is provided at GitHub. A mailing list tracks changes to the code. Git access is also available:

git clone