Accessibility scanners vs visitor tests
Every claim links to where we read it · checked 25 Oct 2026
Rule-based scanners such as axe and WAVE read your page’s code and find a large share of issues, but not all of them. In Deque’s data, automated tests found about 57% of issues. A visitor test adds what only shows up when you use the page: keyboard traps, focus you can’t see, and content that breaks at 200% zoom. Some problems still need a person.
Three kinds of tools
| Kind | What it does | What it misses | Examples |
|---|---|---|---|
| Rule-based scanner | Reads the page’s code against WCAG rules: contrast, missing alt text, form labels, page language, headings | Whether a keyboard user can finish a task, whether alt text makes sense, anything that needs judgment | axe-core, WAVE, Pope Tech, Equalize Digital, AccessKit |
| Overlay widget | Adds a script that changes the page in the visitor’s browser, often with a toolbar | The code on your site stays the same. Claims that a widget alone makes a site meet WCAG have drawn regulator action | accessiBe and the FTC |
| Visitor test | Uses the page: presses Tab, zooms, shrinks the screen, opens pop-ups and sends empty forms | How a screen reader reads the page, whether captions are right, and pages it did not visit | untick on paid plans, or a person doing the same by hand |
How much automated scanners find
It depends on how you count. Deque, which makes axe, counted issues in more than 13,000 audited pages and found that automated tests caught 57.38% of them. Deque says the often quoted 20 to 30% comes from counting WCAG criteria instead of issues.
A smaller test by the UK Government Digital Service in 2017 built a page with 143 barriers and ran 10 tools on it. Together the tools found 71%. The best single tool found 41%, counting prompts for a person to check. 42 barriers were missed by every tool.
Tool makers say the same. axe-core marks some results as “incomplete” for a person to review, and the Equalize Digital plugin says no automated tool can make sure a site is fully accessible.
What a visitor test adds
- Keyboard: press Tab up to 60 times to find focus that gets stuck, can’t be seen or hides behind sticky bars and cookie banners.
- Zoom and reflow: zoom text to 200%, widen the spacing and shrink the screen to 320 pixels.
- Motion: look for animation that won’t stop.
- Pop-ups and forms: open dialogs and send empty forms to see whether errors are announced. Nothing is ever sent to your server.
- Judgment calls: an AI review of alt text, vague links, headings and labels. Its findings are marked “likely”.
untick runs the automatic WCAG 2.2 A and AA rules on every plan. The light check covers 25 pages on Free, 250 on Starter and 500 a site on Pro and Agency. The visitor test runs on paid plans, with a map of all 55 WCAG 2.2 A and AA criteria. How the check works.
What untick can’t tell you
- Whether a screen reader’s reading order makes sense, or a caption is accurate. These go into a guided checklist for your team.
- Pages behind a login, except a few on Pro and Agency.
- Pages outside the ones your plan covers.
- Whether your site meets the law. An automated check shows risk with evidence. It isn’t a certificate.
Sources for the numbers and tools on this page
- Automated tests identified 57.38% of total issues, counted by issue volume, across 13,000+ pages and nearly 300,000 issues.Deque: Automated testing coverage reportChecked
- “With axe-core, you can find on average 57% of WCAG issues automatically.” Results it can’t be sure of are returned as “incomplete”.axe-core README on GitHubChecked
- 10 tools on a page with 143 barriers found 71% together, 41% at best for one tool (counting prompts for a person to check); 42 barriers were missed by all.GOV.UK accessibility blog, 24 Feb 2017Checked
- WAVE, from WebAIM, finds many WCAG errors and “facilitates human evaluation”.WAVE by WebAIMChecked
- Pope Tech is a site-wide platform powered by WAVE.Pope Tech homepageChecked
- Accessibility Checker by Equalize Digital scans WordPress posts and pages and says no automated tool can ensure a site is fully accessible.WordPress.org plugin pageChecked
- AccessKit checks Shopify themes against WCAG 2.1 AA rules and says it is not an overlay.AccessKit on the Shopify App StoreChecked
- The FTC approved a final order on 22 April 2025 requiring accessiBe to pay $1 million over claims that accessWidget could make any website meet WCAG.FTC press releaseChecked
Spotted something out of date? Write to hello@untick.io and we’ll re-check it and update the date.
Questions
What share of accessibility issues do automated tools find?
In Deque’s data, automated tests found 57% of issues by count. In a 2017 UK government test, the best single tool found 41% of 143 barriers, counting prompts for a person to check.
Is an accessibility overlay enough?
An overlay changes the page in the visitor’s browser but not your site’s code. In 2025 the FTC ordered accessiBe to pay $1 million over claims that its widget could make any site meet WCAG.
Does untick replace a manual audit?
No. It covers the automatic rules and the parts a browser can test like a visitor. Screen reader and caption checks still need a person.
Which WCAG version does untick check?
WCAG 2.2, Level A and AA.
Not sure? Run it on your homepage.
The free scan takes about a minute and shows the evidence. No signup.