Accessibility audit tools compared: what axe, WAVE, and Lighthouse catch, and what they miss
Gideon Awolesi ·
Free automated tools are the first thing a lot of teams reach for when they need to check accessibility, and they should be. They're fast, they're free, and we use them on every audit. But they can only find the problems a machine can detect. Here's what the three most common ones do, and what the research says about how much they catch.
01The three tools
| Tool | Made by | How you use it |
|---|---|---|
| axe | Deque | A browser extension and the axe-core library, which you can run in your tests |
| WAVE | WebAIM, at Utah State University | A browser extension that marks problems on the page |
| Lighthouse | Built into Chrome DevTools, and its accessibility checks run on axe-core |
Lighthouse uses axe-core for its accessibility audits, but doesn't run every axe rule, so running axe itself usually finds more.
02How much automated tools catch
In 2021, Deque analysed more than 2,000 of its own audits and found that automated testing identified 57% of the issues by volume. That measures how many of the problems found were automatically detectable, not how many WCAG success criteria a tool can test, and it's a vendor's own data.
In 2017, the UK Government Digital Service built a page with 143 accessibility barriers and ran ten tools on it. All the tools together found about 71% of them, and the best single tool found 41%.
03What they miss
A tool can tell you an image has no alt text. It can't tell you if the alt text that's there is useful. The same goes for a lot of problems:
- If the focus order makes sense as you tab through the page.
- If an error message is announced to a screen reader when it appears.
- If a custom dropdown or date picker can be used with a keyboard.
- If a link that says "Read more" makes sense out of context.
- If a time limit gives people enough time.
04How we use them
We run the automated tools first, fix what they find, and then test the key journeys by hand with a keyboard and a screen reader. The tools clear the obvious problems quickly, so the manual testing time goes on the ones only a person can find. If you've never checked your product, do the same: run a free scan, and fix what it finds.
Then, for the journeys that make you money, pay for manual testing. Our Accessibility Audit tests up to five key journeys by hand against WCAG 2.2 AA in two weeks, from €2,500.