The W3C Markup Validation Service is a free service that checks Web documents in formats like HTML and XHTML for conformance to W3C Recommendations and other standards.

Validate Your Markup

Validate by URL

Enter the URL of the page you want to check. Advanced options are available from the Extended Interface.


Validate by File Upload

Select the file you want to upload and check. Advanced options are available from the Extended File Upload Interface.

Note: file upload may not work with Internet Explorer on some versions of Windows XP Service Pack 2, see our information page on the W3C QA Website.


Validate by Direct Input

Input the markup you would like to validate in the text area below:


Only complete documents (along with a Doctype declaration) will be validated. Advanced options are available from the Extended Direct Input Interface.

Recent Updates

2004-07-23: Markup Validator v0.6.7 Released
Released version 0.6.7, a maintenance release that fixes a few minor bugs, improves authentication proxying, and makes some slight tweaks to the website style and markup.
2004-05-21: Markup Validator v0.6.6 Released
Released version 0.6.6, a maintenance release that fixes a few minor bugs, resurrects the whitespace-preserving source display, adds explanations for additional error messages, and makes some slight tweaks to the website style.
2004-05-07: Markup Validator v0.6.5 Released
Released version 0.6.5, a maintenance release easier to use and install, featuring new documentation, simpler navigation, new recovery mechanisms instead of fatal errors, and offering explanations in addition to error messages.

These are the most recent major changes to this service. See "What's New" for more details.