WCAG accessibility: what automation finds and what it misses

Automated tests cover about a third of the WCAG criteria. What they catch, what they miss, and how to check the rest by hand in half an hour.

Accessibility · Published: 24 June 2026 · 3 min read · Ольга Мирошник

Automated accessibility checks are a good first-pass filter and a poor guarantee. Estimates put their coverage at 25–40% of the WCAG 2.2 criteria. The rest needs a person, because a machine does not understand meaning.

What automation finds reliably

• Images without alt.
• Insufficient contrast between text and background (level AA — 4.5:1 for body text, 3:1 for large text).
• Form fields without an associated <label>.
• Gaps in the heading hierarchy: an H2 straight after an H4.
• Duplicate id values and invalid ARIA roles.
• A missing lang on the document.

These are cheap fixes and they belong in CI: wire axe-core into the e2e run and fail the build on critical violations.

What the machine will miss

Meaningful alt text. alt="image" passes the check and carries nothing. For decorative graphics the right answer is an empty alt="", not a missing attribute.

Focus order. Tabbing must follow the visual order. A modal has to trap focus and return it to the triggering button on close. Neither rule is checkable statically.

Link meaning out of context. Twenty "Learn more" links on a page are valid HTML and useless navigation for a screen reader.

Dynamic updates. A form error appears or the cart counter changes — that needs aria-live, otherwise the change goes unannounced.

Keyboard traps. A custom select or carousel you cannot tab out of.

A thirty-minute manual pass

1. Put the mouse away. Walk the key flow with the keyboard only: Tab, Shift+Tab, Enter, Esc, arrows.
2. Make sure focus is always visible. outline: none without a replacement is the single most common failure.
3. Zoom to 200%. Nothing should be clipped or pushed off screen.
4. Turn on a screen reader (VoiceOver, NVDA) and listen to the first minute of the homepage.
5. Check the page in high-contrast mode and with images disabled.

Why this is not only about disabled users

Correct headings help search engines, label enlarges tap targets on mobile, and a visible focus ring saves time for anyone filling in a form from the keyboard. Accessibility almost always coincides with ordinary interface quality — its failures are simply more visible and more painful.

And fix the target level: WCAG 2.2 AA is the practical reference point most regulatory requirements point to, European ones included.