About Web Content Accessibility Guidelines (WCAG) 2.0

Background of WCAG 2.0

WCAG 2.0 is the document the World Wide Web Consortium (W3C) recommends for improving accessibility of web content for people who are disabled. It was published in 2008 as a stable, referenceable technical document. While it is a thorough collection of technical standards on accessibility, it cannot capture every single component of accessibility and usability.

Level of Conformance

There are 3 levels of conformance, A, AA, and AAA. A website must comply with all the success criteria at level A, should comply with all the success criteria at level AA, and may comply with the success criteria at AAA, recognizing that not all content will be able to comply with AAA. CU Boulder aims to meet the AA level of conformance.

How WCAG 2.0 Is Organized


There are 4 basic principles for web design.

  • Perceivable
  • Operable
  • Understandable
  • Robust


You want your user to be able to PERCEIVE your content with their senses. The most common way is with vision, but it is also possible to PERCEIVE with hearing and touch. If you design your content properly, the user can select the appropriate technology to access it with sight, sound, or touch.


You want users to be able to navigate and use your content, you want it to be OPERABLE. The most common way to OPERATE a webpage or app is with a mouse, but there are other devices such as a keyboard. If you design your content properly, users can select how they approach your content in a variety of situations and with a variety of devices.


You want a user to be able to UNDERSTAND your content. UNDERSTANDING comes both from being able to comprehend the content and the user interface they have to interact with in order to access your content.


You want your content to be robust so it works on a wide variety of devices, including new and old ones, and so assistive technologies can access the content as well.


The 4 principles are broken down into 12 guidelines. The WCAG 2.0 guidelines for designing web content specifically target making content accessible. The 12 guidelines address text alternative, time-based media, adaptability of content, distinguishability of content, keyboard accessibility, enough time, seizures, navigability of content, readability of content, predictability of page, input assistance, and compatibility.

Success Criteria

The 12 guidelines are broken down into 61 Success criteria. The success criteria contained within the guideline are testable points that are either true or false. If a success criterion is false, it means the website or application violates WCAG 2.0.


There is a document with techniques for how a developer can solve specific accessibility problems related to every success criteria. They are possible solutions, but they do not have to be used in order to be WCAG 2.0 compliant. Any approach that makes a success criterion true is acceptable. In this database, we focus on the WCAG 2.0 compliance and issue side, so we do not address techniques for solving the problem. However, if you go to the online WCAG 2.0 documentation, you will find the techniques section.