WCAG Conformance Levels: Understanding A, AA, and AAA

Every success criterion in WCAG is assigned one of three conformance levels — A, AA, or AAA — based on its impact on accessibility and the feasibility of implementation. Understanding these levels is crucial for setting realistic accessibility targets and meeting legal requirements.

Level A: The Baseline

Level A criteria represent the minimum accessibility requirements. Without meeting these criteria, content will be fundamentally inaccessible to significant groups of users. WCAG 2.2 contains 32 Level A criteria.

Level A criteria address the most severe barriers — content that literally cannot be used at all without these accommodations. Examples include providing alt text for images (without which blind users receive no information about the image), making all functionality keyboard accessible (without which users who cannot use a mouse are completely locked out), and avoiding content that could cause seizures.

A website that does not meet Level A has critical accessibility gaps that prevent basic usage by many people with disabilities.

Level AA: The Recommended Standard

Level AA criteria go beyond the baseline to create a meaningfully accessible experience. WCAG 2.2 contains 24 Level AA criteria, and conforming to Level AA means meeting all Level A and Level AA criteria — a total of 56 criteria.

Level AA is the standard referenced by virtually all major accessibility laws worldwide. The European Accessibility Act, through EN 301 549, targets WCAG Level AA. The ADA Title II rule references WCAG 2.1 Level AA. Section 508 references WCAG 2.0 Level AA. The AODA references WCAG 2.0 Level AA.

Level AA criteria address barriers that significantly hinder accessibility but may not completely prevent access. Examples include sufficient color contrast (users with low vision may struggle but could potentially still read low-contrast text), text resizing capability, consistent navigation, and meaningful heading structures.

Level AA should be the target for all organizations. It represents the global consensus on what constitutes adequate digital accessibility.

Level AAA: The Highest Standard

Level AAA criteria provide the highest level of accessibility. WCAG 2.2 contains 30 Level AAA criteria, and full AAA conformance means meeting all 86 criteria across all three levels.

However, W3C explicitly states that it is not possible to achieve Level AAA conformance for all content. Some AAA criteria are mutually exclusive depending on the type of content, and others set standards that are impractical for certain types of content. For example, the AAA reading level criterion requires content to be understandable at lower secondary education level, which may not be achievable for specialized medical or legal content.

Level AAA is not required by any current legislation. Organizations should implement AAA criteria where feasible, as each additional criterion improves accessibility for some group of users, but should not set full AAA conformance as their target.

Examples of Level AAA criteria include enhanced color contrast of 7:1, sign language interpretation for video content, extended audio descriptions, and fully visible focus appearance.

Conformance Requirements

WCAG defines five requirements that must be met to claim conformance at any level:

Requirement 1: All success criteria at the claimed level are satisfied for the full page. Accessibility cannot be claimed for part of a page.

Requirement 2: Entire pages conform. If a page contains content that fails a criterion, the entire page fails, even if most of the page is accessible.

Requirement 3: If a process consists of multiple steps (such as a checkout flow), all pages in the process must conform. It is not sufficient if only some steps are accessible.

Requirement 4: Only accessibility-supported ways of using technologies are relied upon. Technologies used must work with assistive technologies.

Requirement 5: Technologies that are not accessibility-supported may be used as long as they do not block access to the rest of the page, and the page as a whole meets all conformance requirements without them.

Choosing Your Target Level

For virtually all organizations, the answer is clear: target WCAG 2.2 Level AA. This meets current legal requirements, aligns with global best practice, and provides meaningful accessibility for the vast majority of users with disabilities. Implement Level AAA criteria where they are feasible and where they would particularly benefit your users, but do not let the pursuit of AAA delay the achievement of AA.