Can automated scanners find all accessibility issues?
In short: No. Automated scanners reliably detect machine-testable failures — missing alt text, unlabelled inputs, a missing page language, empty links — but commonly cited industry estimates put their coverage at roughly 30–40% of WCAG issues. Whether alt text is meaningful, focus order is logical or a screen-reader flow is usable still needs a human. A clean scan is not proof of compliance.
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What automation does well
- Missing or empty alternative text, form labels, button and link names.
- Missing page language or title, duplicate IDs, broken ARIA references.
- Structural problems such as skipped heading levels or zoom being blocked.
- Checking the same rules on every release, so regressions are caught quickly.
What needs a human
- Whether alt text, labels and headings actually describe the content.
- Logical focus order, keyboard traps and custom widgets that only look interactive.
- Screen-reader experience across a whole flow, such as checkout.
- Captions quality, cognitive clarity and error recovery.
How to use a scanner honestly
Use it as the first pass and as a regression monitor, claim only what you have verified, and plan manual audits of key templates and flows. The W3C also notes that tools can assist an evaluation but cannot determine accessibility on their own.
Official sources
- W3C WAI — Selecting web accessibility evaluation tools
- W3C WAI — WCAG-EM evaluation methodology
- W3C — Web Content Accessibility Guidelines (WCAG) 2.1
See where your site stands
Our free automated scan checks your page against machine-testable WCAG 2.1 AA rules in about 20 seconds — no signup, no overlay.
Scan your site free →Why do scanners give different scores for the same page?
Can AI replace manual accessibility testing?
General information, not legal advice. National transposition laws differ — consult a lawyer for a binding assessment of your business.
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