What no accessibility plugin can check

Automated testing is genuinely useful and genuinely limited. This page is the long version of the one-paragraph disclaimer most tools bury in a footer.

What a scanner can see

A scanner reading your HTML can reliably find mechanical faults: an <img> with no alt attribute, a link whose only content is an icon, a button with no text, an input with no label, a heading that jumps from h1 to h4, a table with no header cells, an iframe with no title, two elements sharing an id, a viewport tag that blocks zoom. These are objective: either the attribute is there or it is not. That is why a scan is worth running — roughly a third of the issues that real audits flag are of this kind, and they are the cheapest to fix.

What a scanner cannot see

• Colour contrast. It depends on computed styles, images, states and text size. A tool can only tell you about colours it can actually resolve, and most claims to the contrary are guesses.
• Whether alt text is any good. A scanner knows an alt attribute exists. It cannot know whether "IMG_2481.jpg" was replaced with something useful, or whether decorative images were correctly left empty.
• Keyboard order in practice. Markup order, CSS, sticky elements, modals and menus decide this, and they only exist once the page is rendered and interacted with.
• Screen reader experience. Whether a page makes sense when read aloud — names, roles, states, announcements after a form submits — is a human judgement.
• Reading order and meaning. A page can pass every check and still be nonsense for someone using assistive technology.
• Cognitive load, plain language, timing, motion. All real accessibility issues, none of them mechanical.

Why "overlay" widgets deserve suspicion

An overlay is a script that adds buttons and fixes on top of your site. It does not change the underlying page, so the original problem remains for anyone whose tools ignore the overlay — which is most of them. It also tends to promise a legal outcome that only a court can decide. Several overlays have been the subject of lawsuits rather than a defence against them. If a vendor tells you a script makes your site compliant, the useful question is: compliant for whom, verified by whom?

How to use a scanner without fooling yourself

1. Run it, fix the mechanical issues, run it again until the list is small. That part is real progress.
2. Read the remaining list out loud, on a phone, using a screen reader for ten minutes. You will learn more than from any report.
3. Test the things that matter most: can you complete your main task with only a keyboard? Can you pay, book or contact with the screen off?
4. Get a person with a disability to try the flow you care about. (Contrast has its own guide here.) Pay them for their time.
5. Write the fixes into your process, so the same problems do not come back next month.

Where this leaves tools like ours

We built AccessAudit to find only what it can prove: a specific list of HTML-level problems, each quoting the exact markup responsible, with no score, no badge and no claim of conformance. If a tool hands you a percentage and a certificate, that is marketing. If it hands you the line of HTML that is wrong, that is something you can act on.