Website accessibility checkers: the free tools

An accessibility checker is a tool that scans a web page and reports where it fails accessibility standards. The useful ones are free. The important thing to understand before you run any of them is that automated testing finds roughly a third of real accessibility problems, so a clean report is a floor rather than a pass mark.

Here is what each of the main free checkers is actually good at, what none of them can see, and the order we would run them in.

The free checkers worth using

What the scanners cannot see

This is the part that matters, and it is why we treat a clean report with suspicion.

• Whether alt text is any good. A tool can see that an image has an alt attribute. It cannot tell that yours says “IMG_4471” or “photo”.
• Whether link text makes sense. It will not flag eleven identical “read more” links, because technically each one has text.
• Whether the tab order is sensible. Everything can be reachable and still jump around the page in a nonsensical sequence.
• Whether error messages are understandable. A form can be technically labelled and still tell you nothing useful when it fails.
• Whether headings describe the content. A tool checks the order of H1 to H3. It does not check that they mean anything.
• Whether a video’s captions are accurate. Automatic captions frequently are not.

The empty alt attribute, which tools get wrong constantly

Worth its own section, because it produces more false alarms than anything else.

A decorative image, a background shape, a divider, an avatar that adds nothing, should have an empty alt attribute, written as alt="". That tells a screen reader to skip it rather than announce a filename. It is correct, it is deliberate, and it is what the standard asks for.

Plenty of automated reports flag every empty alt as a missing alt. We had exactly this on our own site: an audit tool returned over a hundred “missing alt text” rows, and every one of them was a decorative avatar correctly marked as decorative. If your report is full of these, check a few by hand before you spend a day fixing something that was already right.

The order we would run them

1. Tab through the page first, before any tool. Start at the top and press Tab. Can you reach the menu, the links and the form? Can you always see where you are? Can you escape a popup? This finds the worst problems in about two minutes.
2. Run WAVE on your homepage and your contact page. Those two pages carry most of your traffic and all of your enquiries.
3. Run axe DevTools on the same pages to sort the real faults from WAVE’s warnings.
4. Check your body text contrast in the WebAIM checker. Body text needs a ratio of at least 4.5 to 1. Large text can go to 3 to 1.
5. Zoom to 200 percent and see whether anything overlaps or disappears.
6. Read your own link text and count the “click here”s.

That is most of an afternoon at the outside, and it will find nearly everything that is actually stopping people using your site.

A note on overlay widgets

You will be offered tools that promise compliance from a single line of script added to your site. We would avoid them.

They are widely criticised by disabled users and by accessibility professionals, they do not fix the underlying markup, and they have not prevented legal claims. Some actively interfere with the screen readers people already use. Fix the site rather than covering it.

What a clean report does and does not mean

A clean automated report means you have no obvious machine-detectable faults. That is worth having and it is not nothing.

It does not mean your site is accessible, and it is not a defence. Under the Equality Act 2010, service providers must make reasonable adjustments so disabled people are not put at a substantial disadvantage, and that covers websites. The standard normally aimed at is WCAG 2.2 at level AA. If you are selling to EU customers, the European Accessibility Act has applied since 28 June 2025 and can reach UK businesses.

If you want to state your position publicly, an accessibility statement that admits what is not yet right is worth far more than boilerplate claiming full compliance you have not tested for.

How we put this together

These are the tools we use on client sites and on our own. The strengths and weaknesses are from running them rather than from their marketing, and the section on empty alt attributes comes from an audit of our own site that was substantially wrong.

The one third figure for what automated testing catches is the widely cited industry estimate. Treat it as a rough order of magnitude rather than a precise measurement, because it varies enormously with the site.

The short version

Use WAVE to see problems, axe to confirm they are real, the WebAIM checker for contrast, and your keyboard for everything the scanners miss. Ignore the overlay widgets. Check empty alt attributes by hand before fixing them. And treat a clean report as the start of the job rather than the end of it.

For what good and bad actually look like on a page, see website accessibility examples. Accessibility overlaps almost entirely with usability, so the same work shows up in making a website mobile friendly and in our website audit checklist.

If you would rather someone went through your site properly, including the parts a scanner cannot see, send us the address and we will tell you what we find. On a new build it is included as standard in web design for small business rather than priced as an extra.

Sources

• W3C Web Accessibility Initiative, WCAG: the standard and its levels.
• GOV.UK, Equality Act 2010 guidance: the duty to make reasonable adjustments.
• European Accessibility Act: in effect from 28 June 2025.
• WebAIM Contrast Checker: the contrast ratios quoted.