Check whether any website is W3C compliant

Screenshot of Sitebeam's W3C compliance test

Why is it important?

W3C are the primary standards body for the web, and have defined a precise specification for how the HTML (or XHTML) of a website should be written to ensure compatibility, accessibility and follow best practice. W3C compliance is therefore a widely adopted test with many benefits.

As a general rule, sites which are W3C complaint will:

  • work more consistently across web browsers
  • be more accessible and usable
  • work on non-standard devices, such as mobile phones and televisions
  • generally rank better in search engines.

W3C compliance is considered one of the best assurances that the website has been built with accessibility in mind (which is a legal requirement in many countries).

How is it measured?

The W3C test is run on every single page of the website in turn. The overall score is based on the proportion of pages which contain no errors – a perfect score means 100% of pages are compliant.

Although this test reports W3C warnings and errors, only errors count towards the final score. It is therefore possible for a site to score a perfect 10 and yet report compliance warnings.