How Much of WCAG an Automated Scanner Actually Catches
A team runs axe and Lighthouse against a new feature, gets zero reported issues, and wants to skip manual testing entirely on the strength of that clean scan.
Roughly what fraction of WCAG issues do automated tools typically catch?
The correct answer is "About 30-40%."
Automated tools like axe, Lighthouse's accessibility audit, and WAVE are a fast first pass and typically catch on the order of 30-40% of WCAG issues — missing alt text, insufficient contrast, missing form labels, invalid ARIA usage — but they can't evaluate whether a label is meaningful, whether a tab order is logical, or whether an interaction genuinely makes sense with a screen reader running.
Neither "about 90%" nor "100% — all of them" reflects the real coverage gap that makes manual keyboard-only and screen-reader passes non- optional. "About 5%" understates automated tools' real, genuine value as a fast first pass.
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