WCAG Level A, AA and AAA: what “AA” actually means
Almost every accessibility requirement you'll read says “WCAG 2.1 AA” or “WCAG 2.2 AA”. Here is what the letters mean and what it takes to meet them.
Success criteria and levels
WCAG is made of testable rules called success criteria, grouped under four principles: perceivable, operable, understandable and robust. Each criterion has a number, such as 1.4.3, and a level.
The levels stack. Level A is the minimum: without it, some people can't use the page at all. Level AA adds the criteria that remove the most common serious barriers, such as low contrast, missing captions on live video and text that can't be resized. Level AAA is the strictest, with criteria like sign language for video and a 7:1 contrast ratio.
What “meets AA” means
To conform at Level AA, a page has to meet every Level A criterion and every Level AA criterion, or provide a conforming alternate version. There's no partial credit: meeting most of them isn't AA.
Conformance is about whole pages, and about complete processes. If a checkout runs over four pages, all four have to conform for any of them to claim it.
Why AA is the usual target
- The Justice Department's 2024 rule for state and local government websites adopts WCAG 2.1 Level AA.
- Section 508, which covers US federal agencies, uses WCAG 2.0 Level AA for web content.
- The European standard behind the EU's accessibility laws builds its web requirements on WCAG 2.1 Level AA.
- Settlements and contracts in private ADA cases usually point to WCAG AA as well.
AAA isn't recommended as a requirement for entire sites. The W3C notes that some content can't meet every AAA criterion. You can still adopt individual AAA criteria where they help your visitors.
Which version?
Versions matter as much as levels. WCAG 2.0 came out in 2008, 2.1 in 2018 and 2.2 in 2023. Each adds criteria, so “2.2 AA” asks for more than “2.1 AA”. If a contract or law names a version, that's your floor. If nothing is named, the W3C recommends the latest.
Our guide to what's new in WCAG 2.2 lists the extra criteria.
Conformance claims and accessibility statements
A formal WCAG conformance claim names the version, the level and exactly which pages are covered, and the date. Most small organizations publish an accessibility statement instead: what standard they aim for, what they know isn't there yet, and how to report a problem. That's honest, useful to visitors, and doesn't overpromise.
Be wary of anyone offering to make a site “ADA certified”. There's no official certification for websites under the ADA.
Practical takeaways
- Aim for WCAG 2.2 Level AA: it covers 2.1 AA too.
- Treat AA as all-or-nothing per page, and fix whole user journeys, not single pages.
- Use AAA criteria selectively where they help, for example larger focus indicators.
- Write an accessibility statement that says where you are, not where you hope to be.
What a scan can tell you about your level
Found automatically
- Failures of the WCAG A and AA criteria that can be tested automatically
- Which criterion and level each problem falls under
Needs a person
- Whether a page fully meets AA: that always needs manual checks too
- Criteria about meaning, such as whether headings and labels are accurate
A clean automated scan is a good start, not proof of AA. A free scan shows which A and AA problems are on a page.