4.1.1 Parsing (Level A)

Make sure your website uses correct markup and is free of errors that may create usability problems.

What you need to know

The code that comprises our website or mobile app is interpreted by browsers, screen readers, and other assistive technologies. If the code has errors, it can negatively affect the performance of a website.

What you need to do

  • Check and fix your code so that it’s free from errors such as missing closed brackets, duplicate attribute IDs, or broken links.
  • Make sure all elements have start (open) and end (close) tags.
  • Have all HTML elements nested correctly.
  • Make sure elements don’t contain duplicate attributes.
  • Ensure element IDs are unique.


Read the full explanation of success criterion 4.1.1 on

Related Resource

Check out these “Common Failures for SC 4.1.1” from W3C’s Web Accessibility Initiative for more information about this success criterion.