About This Service

The W3C MarkUp Validation Service checks HTML documents for conformance to W3C HTML and XHTML Recommendations and other HTML standards. Related resources include:

• Source code availability.
• The TODO list for The W3C MarkUp Validation Service.
• The www-validator mailing list.
• How to provide feedback on The W3C MarkUp Validation Service.

Other resources

Credits

The W3C MarkUp Validation Service was created and maintained by Gerald Oskoboiny. In a previous incarnation it was known as "The Kinder, Gentler, HTML Validator", but has since found a new home at W3C, and is now maintained under the auspices of the Quality Assurance Activity.

This service uses:

• A derivative version of James Clark's excellent SGML (and XML) parser SP. The version in use for this service is the "OpenSP" version from the OpenJade team. For some time it also made use of Liam Quinn's modified version, lq-nsgmls.
• The LWP Perl Modules by Gisle Aas and Martijn Koster for retrieving documents.
• Documentation and Error Explanations originally written by Scott Bigham.
• Open source software including Apache, Perl, and Debian GNU/Linux.
• Patches and ideas from:
  • Aaron Swartz
  • Björn Höhrmann
  • Christian Smith
  • Dan Connolly
  • Hugo Haas
  • Jim Ley
  • Karl Dubost
  • Liam Quinn
  • Martin Dürst
  • Nick Kew
  • Olivier Thereaux
  • Sean B. Palmer
  • Terje Bless
  • Ville Skyttä
  • ...and the nice people on www-validator@w3.org.