Guide · Regulation Watch
What an automated accessibility check misses
Automated accessibility scanners are useful and fast, but they cannot check much of what matters. Here is what they cannot check, and what a person has to test.
The short answer
Automated checks catch measurable problems such as missing alternative text attributes and some contrast failures. They cannot tell whether alternative text is meaningful, whether a page makes sense with a keyboard or a screen reader, or whether content still works when zoomed. Those need a person.
What tools do well
Scanners find missing labels, empty links, missing language attributes and colour pairs below the contrast ratios in WCAG. They are quick and repeatable, and worth running on every release.
What they miss
- Whether text alternatives actually describe the image.
- Whether the keyboard order makes sense and focus is always visible.
- Whether headings and link text work for a screen-reader user.
- Whether text can be enlarged to 200% and content reflows on a 320-pixel-wide screen without sideways scrolling.
- Whether motion can be paused, and errors are explained next to the field.
A worked example
The colour contrast checker tests colour pairs against WCAG 2.2: body text needs 4.5:1, large text 3:1 and interface parts 3:1. In the worked example, a grey caption at 3.45:1 fails, and so does a pale button border at 1.55:1. The manual worksheet then records what a person actually tested, and what was never tested.
Conformance claims
Claim conformance only for pages and states you have tested, by hand and with tools. “We ran a scanner” is not an audit.
What this guide does not cover
This guide covers common checks, not the full WCAG 2.2 success criteria.
Sources
Responsible for this guide
Examples in this guide are illustrative, not client results. Figures come from the free tool’s worked example; change the inputs in the tool to see your own.
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