WCAG conformance levels — A, AA, and AAA — rank how thoroughly a website meets the Web Content Accessibility Guidelines. A is the minimum, AA is the standard nearly every law and lawsuit references, and AAA is the strictest. The levels stack: to claim a level you must satisfy it and every level beneath it.
What the three WCAG conformance levels mean
The W3C assigns each WCAG success criterion to a single conformance level. The levels aren’t separate checklists you choose between — they nest. Higher levels include everything below them.
- Level A — the most basic, must-have requirements. Failing them makes a site impossible or extremely difficult to use for some people. There are 30 Level A criteria in WCAG 2.1.
- Level AA — addresses the biggest and most common barriers. AA is where “accessible enough for the real world, and for the law” lives. WCAG 2.1 AA adds 20 criteria on top of A, for 50 total.
- Level AAA — the highest, strictest level. It adds another set of criteria for the most robust possible experience, but the W3C explicitly says it can’t always be met across an entire site.
A key rule trips people up: conformance is cumulative. You can’t conform to AA while skipping a Level A criterion. To say a page meets AA, every A and AA criterion that applies must pass. To meet AAA, the A, AA, and AAA criteria must all pass.
| Level | Criteria (WCAG 2.1) | What it removes | Practical role |
|---|---|---|---|
| A | 30 | Total blockers (no alt text, no keyboard access, no captions on video) | The floor — necessary but not sufficient |
| AA | 50 (30 A + 20 AA) | Major barriers: low color contrast, no visible focus, missing labels, no reflow | The legal and procurement standard |
| AAA | 78 (50 + 28 AAA) | Remaining friction: stricter contrast, sign language, no timing limits | A stretch goal, not a site-wide mandate |
All of these criteria are organized under the four POUR principles — Perceivable, Operable, Understandable, and Robust — so the level tells you how strict, while POUR tells you what kind of barrier each criterion addresses.
Why Level AA is the target for legal compliance
If you remember one thing: for U.S. businesses, the level that matters is AA — specifically WCAG 2.1 AA. Not A, and not AAA. Every major signal points to AA:
- The DOJ has repeatedly cited WCAG conformance in ADA settlement agreements, and its 2024 Title II rule for state and local governments sets WCAG 2.1 AA as the technical standard.
- Section 508, which governs federal agencies and their vendors, incorporates WCAG 2.0 AA by reference. The Section508.gov guidance treats AA as the bar, and a VPAT reports conformance against AA criteria.
- Plaintiffs’ attorneys in ADA Title III cases measure private websites against WCAG 2.1 AA. Thousands of ADA web lawsuits and demand letters are filed each year, and AA is the yardstick used in nearly all of them.
So why not A? Because Level A leaves out the criteria that actually cause complaints — sufficient text contrast (1.4.3), visible keyboard focus (2.4.7), reflow on small screens (1.4.10), and status-message announcements (4.1.3) all live at AA. A site that meets only Level A can still be unusable for someone with low vision or a motor disability, and still draws lawsuits.
The ADA itself doesn’t name a WCAG version number for private businesses, so AA is the consensus benchmark rather than a line of statute. None of this is legal advice — for your specific exposure, consult an attorney. For how these frameworks fit together, see ADA vs Section 508 vs WCAG.
What AAA adds — and why it isn’t required site-wide
Level AAA exists for organizations that want to go beyond the standard, or for content serving audiences with specific needs. It tightens criteria you already met at AA and adds new ones:
- Contrast (Enhanced) 1.4.6 raises the color-contrast ratio for normal text from 4.5:1 (AA) to 7:1.
- Sign Language (Prerecorded) 1.2.6 requires sign-language interpretation for prerecorded audio.
- No Timing 2.2.3 removes time limits on interactions entirely.
- Reading Level 3.1.5 asks that content not require more than a lower-secondary education reading level, or that a simpler version be provided.
- Three Flashes 2.3.2 bans any flashing content, stricter than the AA threshold.
Here’s the catch the W3C states directly: “It is not recommended that Level AAA conformance be required as a general policy for entire sites because it is not possible to satisfy all Level AAA Success Criteria for some content.” A news site can’t always provide a sign-language video for every audio clip; a technical manual can’t always hit a lower-secondary reading level. That’s why AAA is best applied selectively — to a specific page, flow, or audience — rather than declared across an entire site.
Targeting AAA before you’ve nailed AA is a common mistake. Get the 50 AA criteria solid first; treat AAA as polish.
How conformance is measured (and why scanners can’t tell you)
A conformance level is a claim about every applicable criterion at that level passing on a page. That’s a higher bar than “the scanner found no errors.”
Automated tools and overlay widgets reliably detect only about 30–40% of WCAG issues. The criteria that decide whether you actually reach AA — keyboard traps, broken focus order, unlabeled custom widgets, missing form labels — almost always require a person testing with a keyboard and a screen reader like NVDA, JAWS, or VoiceOver. That gap is exactly why a paste-in script can’t certify a level. It’s also why overlays don’t ensure ADA compliance: they can’t perform the human judgment AA conformance demands, and many sites running them still receive demand letters. If you’re weighing options, compare overlay versus manual remediation.
Confirming your level follows a clear path:
- Audit against AA. Test every Level A and AA criterion — automated plus manual. A professional accessibility audit produces a prioritized list of where you fall short.
- Remediate the code by hand. Fix the underlying HTML, CSS, and ARIA so each criterion genuinely passes. Manual accessibility remediation is the only durable way to move from “fails AA” to “meets AA.”
- Verify and document. Re-test, then record the result in an accessibility statement or a VPAT, which states the level and version you conform to.
For background reference on the criteria at each level, WebAIM maintains an excellent plain-language WCAG checklist.
Choosing your target level
For a small business, the decision is simple:
- Target AA across the whole site. It satisfies the law, procurement requirements, and the vast majority of users. This is the goal for almost everyone.
- Reach for AAA only on specific content where it’s feasible and valuable — a key landing page, a video library, a flow used heavily by people with cognitive disabilities.
- Never settle for A. It’s the floor, not a finish line, and it won’t protect you from a lawsuit.
Curbcut does the manual work to get sites to WCAG 2.1 AA — no widgets, no shortcuts. The fastest way to learn which level you currently meet is a free accessibility scan, and from there a full audit maps out exactly what stands between you and AA.
The short version
WCAG defines three nested conformance levels: A (minimum), AA (the standard U.S. courts, the DOJ, and Section 508 expect), and AAA (strictest, not required site-wide). Conformance is cumulative — AA includes all of A, and AAA includes all of AA. For nearly every business, AA is the level to hit, and reaching it takes manual remediation, not an overlay.