Check the markup (HTML, XHTML, …) of Web documents This form allows you paste complete HTML documents and have them validated.

Supported document types include the HTML (through HTML 4.01) and XHTML (1.0 and 1.1) family, MathML, SMIL and SVG (1.0 and 1.1, including the mobile profiles). The Markup Validator can also …

This validator checks the markup validity of Web documents in HTML, XHTML, SMIL, MathML, etc. If you wish to validate specific content such as RSS/Atom feeds or CSS stylesheets, MobileOK …

Here you will find the documentation for The W3C Markup Validation Service. We are constantly working on improving this documents and adding new elements, and eagerly welcome feedback and additions!

It compares your HTML document to the defined syntax of HTML and reports any discrepancies. Learn more about the Markup Validator and the languages it can validate.

About W3C Validation services W3C provides various free validation services that help check the conformance of Web sites against open standards. You are most likely here because this address …

This is the W3C Feed Validation Service, a free service that checks the syntax of Atom or RSS feeds. The Markup Validation Service is also available if you wish to validate regular Web pages.

Your page doesn't validate, and you don't know why, or you have a question about HTML, stylesheets or validation? First, check our Help and FAQ document, as well as the Web authoring FAQ to see if …