WCAG Conformance Levels (A, AA, AAA)

Every WCAG success criterion is assigned one of three conformance levels. The levels are not a difficulty rating and they are not cumulative scores; they express how fundamental a criterion is to accessibility and how feasible it is to satisfy across the full range of web content.

• Level A is the minimum. These criteria address barriers that would otherwise make content impossible for some people to use at all, such as providing text alternatives for images and making all functionality available from a keyboard.
• Level AA addresses the most common and significant barriers and is the level nearly all regulations and legal settlements require. Examples include a 4.5:1 minimum contrast ratio for normal text, visible keyboard focus, and consistent navigation.
• Level AAA is the highest and most stringent level. It includes enhancements like sign-language interpretation for audio and a 7:1 contrast ratio. The W3C itself advises that AAA conformance is not recommended as a general policy for entire sites because some content cannot meet all AAA criteria.

The levels are cumulative in one important sense: to claim Level AA conformance, content must satisfy all Level A and all Level AA criteria. To claim Level AAA, it must satisfy A, AA, and AAA. There is no partial conformance claim for a page under WCAG; if a single applicable criterion at the target level fails, the page does not conform at that level, though you can and should still report and remediate against it.

In practice, Level AA is the operative standard. The Revised Section 508 Standards require WCAG 2.0 Level AA, the U.S. Department of Justice's 2024 Title II rule for state and local governments adopts WCAG 2.1 Level AA, and courts hearing ADA website cases have consistently pointed to WCAG 2.1 or 2.2 Level AA. When someone says a site should be WCAG compliant without naming a level, they almost always mean Level AA.