What is it?
An accessibility audit is the verification step after you've written accessible code. Automated tools (axe, Lighthouse, Pa11y) catch about 30–40% of issues. The rest — focus order, meaningful labels, screen reader flow — needs manual testing with a keyboard and a screen reader. A real audit combines both.
Why it matters
"It should be accessible" is a wish. "It passes axe and I walked it with VoiceOver" is verification. Most teams ship a11y bugs because they never test, only intend. The developer who actually audits — and can teach the team to — is rare and valued, especially at companies with legal a11y requirements.
What to learn
- Automated tools: axe DevTools, Lighthouse a11y, Pa11y CI
- Why automation catches only 30–40% of WCAG issues
- Manual keyboard testing: tab order, focus traps, skip links
- Screen reader testing: VoiceOver (Mac), NVDA (Windows), TalkBack (Android)
- The accessibility tree in devtools
- Color contrast and zoom testing (200% zoom, reflow)
- Writing an audit report that a team will actually act on
Common pitfall
Running Lighthouse, getting 100, and declaring victory. A perfect automated score means the machine-checkable rules pass — not that a blind user can complete the checkout. The 60% automation misses (does the label make sense? is the focus order logical?) is exactly the part that matters most.
Resources
Primary (free):
- Deque — axe DevTools · tool
- web.dev — How to do an accessibility review · docs
- WebAIM — Screen reader testing · article
Practice
Audit a real page in three passes. One: run axe DevTools and fix every flagged issue. Two: unplug the mouse and complete every task by keyboard. Three: turn on VoiceOver or NVDA and complete the same tasks with your eyes closed. Write down every problem each pass surfaced. Done when all three passes are clean.
Outcomes
- Run an automated a11y audit and fix what it flags.
- Complete a manual keyboard pass and find focus-order bugs.
- Use a screen reader well enough to catch labeling problems.
- Write an audit report a team can act on without you.