Accessible Technology

Validating Your Code


Using standards-compliant HTML increases the likelihood that all web browsers and assistive technologies will correctly handle your content. If your code contains errors or tags that are not part of the HTML specification, screen readers and other assistive technologies might fail when trying to render the content for users. Even pages that seem to look fine in a web browser might have unseen problems for assistive technology users.

There are many additional reasons to validate your HTML:

  • Validating mark-up can help in your debugging efforts if your web page exhibits unexpected problems.
  • Valid mark-up provides a better cross-browser, cross-platform, experience and gives you maximum control over how your page is displayed.
  • Valid mark-up will help with future compatibility as it will have the best chance of being backward-compatible with new technologies.
  • Properly formed HTML renders faster than HTML with errors. This means less load on servers and client browsers.
  • A site that validates using proper HTML is a sign of professionalism.


  • Use the W3C Markup Validation Service to check your HTML against current web standards.
  • Use the W3C CSS Validation Service to validate your Cascading Style Sheets.
  • Use Siteimprove, a powerful tool that scans your site at regular intervals for broken links, spelling errors, and accessibility problems. The UW has an enterprise license for Siteimprove. More information will be added to this website soon.


See the Techniques section for links to tools that can be used for testing your site for valid code.