What is WCAG?
WCAG stands for the Web Content Accessibility Guidelines, the international standard for digital accessibility from the W3C — the World Wide Web Consortium, the body that also maintains the standards behind HTML and CSS. It's developed by the W3C's Web Accessibility Initiative (WAI).
WCAG describes what a website has to do so people with disabilities can use it: people who are blind and use a screen reader, people who navigate only with a keyboard, people with low vision who zoom in or need strong contrast, people who are deaf or hard of hearing, and people with cognitive disabilities.
It isn't a style guide or a list of opinions. WCAG is made of success criteria — specific, testable statements that a page either meets or fails. "Text has a contrast ratio of at least 4.5:1" is a success criterion. So is "everything works with a keyboard."
WCAG versions: 2.0, 2.1, and 2.2
WCAG has been updated over time, and each version builds on the last:
| Version | Published | What it added |
|---|---|---|
| WCAG 2.0 | 2008 | The foundation: the four principles and the core success criteria. |
| WCAG 2.1 | 2018 | Criteria for mobile, low vision, and cognitive disabilities — such as reflow, non-text contrast, and text spacing. |
| WCAG 2.2 | 2023 | Focus not obscured, target size, dragging alternatives, consistent help, redundant entry, and accessible authentication. Removed 4.1.1 Parsing as obsolete. |
WCAG 2.2 is the current W3C recommendation. Because it's backward-compatible, a site that meets WCAG 2.2 AA also meets WCAG 2.1 AA.
Conformance levels: A, AA, and AAA
Every success criterion has a level:
- Level A — the minimum. Without these, some people can't use your site at all.
- Level AA — the level courts and most regulations point to. It includes everything in Level A.
- Level AAA — the highest level. The W3C doesn't recommend requiring it for entire sites, because some content can't meet it.
In WCAG 2.2, Levels A and AA together contain 55 success criteria: 31 at Level A and 24 at Level AA. We list and explain every one in our ADA website compliance checklist.
The four principles of WCAG
Every success criterion sits under one of four principles, often remembered as POUR:
- Perceivable — information can be seen, heard, or otherwise perceived: text alternatives for images, captions for video, enough contrast, content that reflows on small screens.
- Operable — everything works with a keyboard, with enough time, without traps, and with a focus indicator you can always see.
- Understandable — content and forms behave predictably, labels are clear, and errors are explained.
- Robust — the code is built so assistive technology like screen readers can read and operate it.
WCAG and the ADA
The Americans with Disabilities Act doesn't list technical rules for business websites. In practice, U.S. courts use WCAG 2.1 Level AA as the benchmark for ADA website compliance, and WCAG 2.2 AA is current best practice. That's why WCAG is the standard to target if your business serves the public in the U.S.
The stakes are real: over 5,000 website accessibility lawsuits were filed in the U.S. in 2025, most against businesses under $25M in revenue. We're engineers, not attorneys — for your specific legal obligations, consult a lawyer.
What "WCAG compliance" means in practice
WCAG compliance — the formal term is conformance — means every page meets every success criterion at your target level. You can't get there with a single automatic scan: no automated tool catches more than 30–50% of WCAG issues.
A proper check combines three kinds of testing:
- Automated engines such as axe-core, pa11y, Lighthouse, and WAVE, to catch the mechanical failures quickly.
- Manual code inspection of markup, ARIA, headings, and focus order.
- Screen-reader and keyboard testing with VoiceOver and NVDA, the way a person with a disability actually uses the site.
Beware of shortcuts. Accessibility overlays promise WCAG compliance with one line of code. They don't change your site's code, and nearly 1 in 4 accessibility lawsuits in 2025 hit sites that already had one. Why overlays don't work.
How to start meeting WCAG on your site
Six errors account for 96% of the WCAG failures found on websites, and they're also the most fixable: low color contrast, missing alt text, missing form labels, empty links, empty buttons, and a missing page language. Start there, then work through the full list.
If you'd rather not do it yourself, we audit your site by hand against all 55 WCAG 2.2 AA criteria, fix every issue in your code, and document it with a before-and-after report.