GSA Government-wide Section 508 Accessibility Program

WCAG 2.0 Conformance

The proposed new standard for Section 508 is expected to require conformance to the W3C Web Content Accessibility Guidelines (WCAG) 2.0 Level AA. But what does this mean? This page poses some specific questions about WCAG 2.0 conformance and provides basic answers to help understand WCAG 2.0 conformance requirements.
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What do the different levels of WCAG 2.0 conformance mean?

The WCAG 2.0 Success Criteria are categorized according to three levels providing successively greater degrees of accessibility:

  • Level A (minimum) – the most basic web accessibility features
  • Level AA (mid-range) – deals with the biggest and most common barriers for disabled users
  • Level AAA (highest) – the highest level of web accessibility

Conformance at a higher level indicates conformance at lower levels, i.e. conformance to Level AA necessarily implies conformance to Level A.

Level A sets a minimum level of accessibility and does not generally achieve broad accessibility for many situations. Level AA is proposed as the new standard for the anticipated refresh of the Access Board Standard for Section 508. The WCAG document does not recommend that Level AAA conformance be required as a general policy because it is not possible to satisfy all Level AAA success criteria for some content.

What does it actually mean to conform to WCAG 2.0?

According to the definition of conformance from the W3C website, there are five requirements that must be met in order for content to be classified as conforming to WCAG 2.0:

  1. "Conformance Level: One of the following levels of conformance is met in full.
    • Level A: For Level A conformance (the minimum level of conformance), the Web page satisfies all the Level A Success Criteria, or a conforming alternate version is provided.
    • Level AA: For Level AA conformance, the Web page satisfies all the Level A and Level AA Success Criteria, or a Level AA conforming alternate version is provided.
    • Level AAA: For Level AAA conformance, the Web page satisfies all the Level A, Level AA and Level AAA Success Criteria, or a Level AAA conforming alternate version is provided."
  2. "Full pages: Conformance (and conformance level) is for full Web page(s) only and cannot be achieved if part of a Web page is excluded."
  3. "Complete processes: When a Web page is one of a series of Web pages presenting a process (i.e., a sequence of steps that need to be completed in order to accomplish an activity), all Web pages in the process conform at the specified level or better."
  4. "Only Accessibility-Supported Ways of Using Technologies: Only accessibility-supported ways of using technologies are relied upon to satisfy the success criteria." This basically says that the way chosen to satisfy the Success Criteria will work with user agents and assistive technologies – meaning essentially that standard methods are used to expose content to assistive technology or special accessibility features in mainstream user agents.
  5. "Non-Interference: If technologies are used in a way that is not accessibility supported, or if they are used in a non-conforming way, then they do not block the ability of users to access the rest of the page." This basically says that technologies that are not accessibility supported can be used, as long as the non-accessibility-supported material does not interfere and all the information is also available using technologies that are accessibility supported.

How did the W3C determine the different levels of WCAG 2.0 conformance?

The basis for assigning a level to a success criteria is described by the W3C in Understanding Levels of Conformance:

"The Success Criteria were assigned to one of the three levels of conformance by the working group after taking into consideration a wide range of interacting issues. Some of the common factors evaluated when setting the level included:

  • whether the Success Criterion is essential (in other words, if the Success Criterion isn't met, then even assistive technology can't make content accessible)
  • whether it is possible to satisfy the Success Criterion for all Web sites and types of content that the Success Criteria would apply to (e.g., different topics, types of content, types of Web technology)
  • whether the Success Criterion requires skills that could reasonably be achieved by the content creators (that is, the knowledge and skill to meet the Success Criteria could be acquired in a week's training or less)
  • whether the Success Criterion would impose limits on the "look & feel" and/or function of the Web page. (limits on function, presentation, freedom of expression, design or aesthetic that the Success Criteria might place on authors)
  • whether there are no workarounds if the Success Criterion is not met”