WCAG Conformance Levels

WCAG defines three conformance levels that indicate how broadly a website satisfies its accessibility requirements: A, AA, and AAA. For frontend engineers, understanding these levels helps translate accessibility requirements into implementation and testing decisions.

WCAG organizes its testable success criteria into three conformance levels: A, AA, and AAA. Level A addresses the most basic accessibility requirements, while AA covers additional barriers and AAA represents the highest level of conformance.

Conformance is cumulative. A page conforming at Level AA must satisfy all applicable Level A and Level AA success criteria, not merely the AA criteria by themselves. Likewise, AAA includes the requirements from the lower levels.

WCAG conformance applies to specific content or pages under defined conformance conditions, rather than being a simple property of an entire technology stack. A frontend engineer should therefore consider the actual rendered interface, its content, and its accessibility behavior when evaluating requirements.

In practice, Level AA is commonly used as the target in accessibility policies and standards-based projects. AAA is not intended as a universal requirement because some AAA criteria cannot reasonably be applied to all content or situations.

The conformance level does not replace individual accessibility testing. Developers still need to inspect semantic HTML, keyboard interaction, names and labels, focus behavior, contrast, and other applicable success criteria.

Key points

• WCAG has three conformance levels: A, AA, and AAA.
• Conformance levels are cumulative: AA includes A requirements, and AAA includes A and AA requirements.
• Level A addresses foundational accessibility barriers.
• Level AA adds broader requirements and is a common target for accessibility compliance.
• Level AAA is the highest level but is not intended as a universal target for every site or piece of content.

Interview questions

If a page meets every AA success criterion, does it automatically meet Level A?

Yes, assuming the applicable conformance requirements have been evaluated correctly. WCAG conformance levels are cumulative, so Level AA incorporates the requirements from Level A. Therefore, a valid AA claim necessarily includes satisfaction of the applicable Level A criteria.

What are the three WCAG conformance levels?

The three levels are A, AA, and AAA. Level A contains foundational requirements, AA adds further requirements, and AAA adds the highest level of requirements. The levels are cumulative, so satisfying AA requires satisfying the applicable A and AA criteria.

What does WCAG Level AA mean for a frontend engineer?

Level AA means the applicable Level A and Level AA success criteria are satisfied for the content being evaluated. For a frontend engineer, this can affect semantic markup, keyboard interaction, focus management, text alternatives, contrast, and other implementation details. It is not enough to implement only the criteria explicitly labeled AA.

Is AAA always better and therefore the correct target?

AAA represents a higher WCAG conformance level, but it is not intended as a universal requirement for every site or type of content. Some AAA criteria are difficult or inappropriate to apply universally. A project should define its applicable accessibility requirements rather than assuming that AAA is always the necessary target.

Why shouldn't developers describe a site simply as 'WCAG compliant' without specifying a level?

WCAG defines multiple conformance levels, so the level provides important context about which requirements were satisfied. A meaningful conformance statement should also identify the applicable version or edition and the scope being evaluated. Without that context, 'WCAG compliant' can be ambiguous.