WCAG, the standard everything else points to.

Four principles, testable criteria

WCAG organizes accessibility under four principles. Content must be perceivable (text alternatives, captions, sufficient contrast), operable (keyboard access, enough time, no traps), understandable (readable, predictable, helpful with errors), and robust (works with assistive technologies). Under each principle sit success criteria: specific, testable statements like "text has a contrast ratio of at least 4.5:1".

What Level AA means

Each criterion carries a level: A, AA, or AAA. Level AA, which includes all Level A criteria, is the bar adopted by the EAA, EN 301 549, US legal practice, and most other frameworks. WCAG 2.1 AA contains 50 success criteria. AAA is aspirational and rarely required in full.

2.1 versus 2.2

WCAG 2.2, published in October 2023, adds nine success criteria to 2.1, six of them at Level A or AA. The additions focus on focus visibility, dragging alternatives, minimum target sizes, accessible authentication, and not asking users for redundant information. One criterion (4.1.1 Parsing) was removed as obsolete. Everything that conforms to 2.2 AA also conforms to 2.1 AA, so targeting 2.2 is the forward-compatible choice; regulation will catch up to it over time.

Automated versus manual testing

Software can reliably verify roughly half the AA criteria: contrast, missing alternatives, name and role of controls, document structure. The rest, such as focus order making sense or error messages being genuinely helpful, needs a human. Complaudax runs the automated half in your browser, including on pages behind a login, and tracks the manual half as a per-site checklist so both are documented. For a working list, see the WCAG 2.1 AA checklist for agencies. To see what the automated half finds on any public page right now, try the free accessibility checker.