What is WCAG? Explained in Plain English
September 24, 2026
What WCAG Is, and What It Is Not
The Web Content Accessibility Guidelines (WCAG) is published by the World Wide Web Consortium (W3C). It is a technical specification written by a working group, not a statute passed by a legislature, which means the WCAG itself is not a law. It is, however, the standard nearly every conversation about ADA compliance ends up pointing to.
The Americans with Disabilities Act (ADA) is a law, but it was signed in 1990 and says nothing about websites. So when plaintiffs began bringing web accessibility claims under Title III, courts needed a technical yardstick, and WCAG was the only credible one available. They have been pointing at it ever since, in orders, settlements, and consent decrees, though the version they name has moved between 2.0 Level AA and 2.1 Level AA. That is how WCAG became the working definition of ADA website compliance without any statute saying so. The Department of Justice went further, adopting WCAG 2.1 Level AA outright as the binding standard for state and local government websites and mobile apps. Section 508 incorporates WCAG 2.0 Level AA for federal agencies. And the European Accessibility Act arrives at WCAG through EN 301 549, the European standard organizations use to show conformance.
The pattern repeats: the laws supply the obligation of accessibility and WCAG supplies the definition of “accessible.” Essentially, WCAG is a voluntary standard cited so consistently that it functions like a regulation.
The Four Principles: POUR
WCAG organizes everything under four principles. These are the guiding ideas behind the success criteria (which we will dive into next).
Perceivable. Users have to be able to detect the content with a sense available to them. Websites that don’t supply alternative text on images or have poor text contrast ratios are not perceivable or digestible to someone using a screen reader.
Operable. Users have to be able to work the interface. If a dropdown only opens on hover, a keyboard user cannot open it. If a carousel advances faster than someone can read it, they cannot use it.
Understandable. Content and behavior have to make sense. A form that rejects a submission without saying which field failed is not understandable.
Robust. Content has to work with the assistive technology people actually use, including newly released versions. This is mostly a question of clean, semantic markup that screen readers and other tools can interpret reliably.
Those four principles encapsulate thirteen guidelines, and under those guidelines sit the success criteria. The success criteria are the testable part, and they are what conformance is measured against.
The Three Conformance Levels: A, AA, AAA
Every success criterion carries a level. Here’s what each one means in plain language.
In WCAG 2.2 there are 86 success criteria total: 31 at Level A, 24 at Level AA, and 31 at Level AAA.
Level A is the floor. These are the failures that block people outright: no alt text, no keyboard access, no form labels, video with no captions. Clearing Level A means you meet those 31 success criteria and your site is usable rather than unusable for a lot of people. It does not mean it is good or easily used, just functional.
Level AA is the working standard. It adds contrast minimums, visible focus indicators, consistent navigation, text resizing, and headings that actually describe what follows. This is the level most settlements and consent decrees land on, the level the DOJ adopted for Title II, the level EN 301 549 requires in the EU, and the level in most procurement documents you will see.
Level AAA is the ceiling. Sign language interpretation for prerecorded audio, a 7:1 contrast ratio, reading level constraints. W3C itself says AAA conformance is not achievable for all content, and no major legal regime requires it site-wide.
The levels stack, and this is where teams get tripped up. Conforming to Level AA does not mean clearing just the 24 criteria in that level. It means clearing all 31 Level A criteria plus all 24 Level AA criteria, so 55 in total. If somebody tells you they hit AA but skipped some A items, they haven’t hit AA.
Short version: aim for Level AA. Treat Level A as the emergency floor and Level AAA as a set of good ideas you adopt if they are practical. AA is the level U.S. courts effectively use to judge ADA website compliance, and the level the DOJ adopted outright for state and local government sites.
The Three Versions: 2.0, 2.1, and 2.2
There are three live versions, and none of them retired the others.
- WCAG 2.0 (2008) is the original. Still valid, still cited in older contracts.
- WCAG 2.1 (2018) added 17 success criteria and one new guideline, mostly covering mobile, low vision, and cognitive accessibility. This is the version named in the DOJ Title II rule and in most current legal obligations.
- WCAG 2.2 (2023, updated 2024) added 9 more criteria, focused on keeping focus visible, click-based alternatives to dragging, minimum target size, and consistent help. It also removed one criterion, 4.1.1 Parsing, which W3C dropped because assistive technology no longer parses HTML directly.
Practically: for most obligations, 2.1 AA is the floor you have to clear. 2.2 AA is the bar to build toward. Some newer procurement language names 2.2, and moving from 2.1 AA to 2.2 AA adds only six criteria.
Putting Versions and Levels Together
A label like “WCAG 2.1 AA” combines both: the number is the version, and the letters are the level. Together they define an exact checklist. WCAG 2.1 AA means every Level A and AA criterion in the 2018 version, 50 in total. WCAG 2.2 AA means every Level A and AA criterion in the 2023 version, 55 in total.
Because each version builds on the last, content that conforms to WCAG 2.2 also conforms to 2.1 and 2.0. Build to 2.2 AA, and you cover the older targets along the way.
Why a Voluntary Standard Has Legal Teeth: WCAG and ADA Compliance
A short tour of where the obligation actually comes from.
ADA Title III (private businesses). No federal regulation names a web standard, and DOJ rulemaking on Title III remains stalled. Courts have filled that space themselves, usually pointing to WCAG 2.0 AA or 2.1 AA, though no version carries the force of law, and circuits still disagree on whether a website with no physical location is even covered. Most settlements land on WCAG 2.1 AA, so that’s the working target. Demand letters and federal filings keep piling up in a handful of jurisdictions.
ADA Title II (state and local government). DOJ’s April 2024 final rule made WCAG 2.1 AA binding for public entity websites and apps. An interim rule in April 2026 pushed the deadlines back about a year: April 26, 2027 for entities serving 50,000 or more people, April 26, 2028 for smaller entities and special districts. The requirement itself didn’t change. DOJ expects to implement the rule on the new timeline unless it proposes changes or extends the deadlines again, and it has signaled plans for further review. Public entities remain bound by the ADA’s existing communication rules in the meantime, and private suits over inaccessible content remain a risk.
Section 508. A federal law covering how agencies develop, buy, maintain, and use technology, all of which must be accessible. The U.S. Access Board sets the standard, not DOJ, and it points to WCAG 2.0 Level AA. Coverage extends past websites to software, documents, and hardware. It binds federal agencies, not private companies, but reaches vendors through their contracts. Sell to a federal agency, and you’ll be asked for a VPAT (Voluntary Product Accessibility Template) documenting how your product conforms.
European Accessibility Act (certain products and services sold in the EU). Enforceable since June 28, 2025. The Directive requires accessibility without defining it technically; that definition comes from EN 301 549, the EU’s technical standard. The current version points to WCAG 2.1 Level AA, but a new version, V4.1.1, was published in September 2026 and moves to WCAG 2.2 Level AA. It becomes the official benchmark once the EU formally cites it, expected by the end of 2026.
Four legal regimes, all built on the same guidelines: WCAG 2.0 AA for Section 508, 2.1 AA for most U.S. obligations, and 2.2 AA arriving in the EU.
What Failing Actually Looks Like
Across the top one million home pages, six failure types account for 96% of all errors automated testing detected. Here is what they are and which criterion each one breaks.
| Failure | % of Home Pages Found On | WCAG Criterion | The Fix |
|---|---|---|---|
| Low contrast text | 83.9% | 1.4.3 Contrast, AA | 4.5:1 for normal text, 3:1 for large |
| Missing alt text | 53.1% | 1.1.1 Non-text Content, A | Meaningful alt; empty alt=”” for decorative images |
| Missing form labels | 51% | 1.3.1 and 4.1.2, A | A real label element; placeholder text is not a label |
| Empty links | 46.3% | 2.4.4 Link Purpose, A | Link text that names the destination |
| Empty buttons | 30.6% | 4.1.2 Name Role Value, A | An accessible name on every control |
| Missing document language | 13.5% | 3.1.1 Language of Page, A | Set lang on the html element |
Source: The WebAIM Million: The 2026 report on the accessibility of the top 1,000,000 home pages
How to Tell Where You Actually Stand
A few things worth being honest about before you go looking.
Page-by-page testing will mislead you. Accessibility failures tend to start in templates, not pages. One CMS theme change can drop the alt attribute pattern across thousands of images at once. Checking your home page and three landing pages tells you almost nothing about the other four thousand. To know where you stand, you have to scan the whole site.
Overlay and “widget” add-ons won’t make your site compliant on their own. In 2025 alone, 22.6% of total accessibility lawsuits were filed against companies using accessibility widgets.
Automated scanning can prove a portion of the criteria. ObservePoint runs 71 automated tests covering 28 WCAG success criteria on every page, across WCAG 2.0, 2.1, and 2.2, and grades findings Critical, Serious, Moderate, or Minor. That is comprehensive for the machine-testable criteria, but it is still only about a third of the full criteria list.
The rest needs people. No scanner can tell you whether alt text is meaningful, whether a custom date picker works with a screen reader, whether focus order makes sense to a human, or whether captions are accurate. Automated scanning is the breadth layer that catches regressions across every page on every release. Manual and assistive technology testing, ideally including people with disabilities, is the depth layer on your highest-value flows.
A score on one date is worth less than a trend. If a demand letter arrives, a dated history demonstrating you were monitoring, prioritizing, and fixing accessibility issues helps. One data point from one day isn’t a strong legal defense. Consistent monitoring creates a defensible history of compliance.
Start Here This Week
- Scan your entire site, not a sample, and record the result as your baseline. Don’t have a way to scan your site? Scan with ObservePoint for free HERE.
- Sort findings by severity, then by where they sit. A missing label on your checkout button is not the same severity as low contrast on a 2019 blog post.
- Fix the Level A failures on your highest-traffic templates first. Most of them are one-attribute changes with site-wide reach.
- Put the scan on a schedule and route the failures to whoever ships code, so issues are surfaced and remediated quickly
- Book manual and assistive technology testing for your top transactional flows. Automation cannot cover them, and those are the flows that get litigated.
If you want baseline metrics without a procurement conversation, ObservePoint’s accessibility scanning is part of the core platform.
