Site-wide accessibility testing
with
AccessLint Core
95 rules mapped to WCAG 2.2, a remediation guide for every one of them, and a crawler that runs them across your whole site — up to 5,000 pages per report.
Included on Pro, Agency and Enterprise plans.
What is AccessLint Core?
An open-source, MIT-licensed engine with 95 rules mapped to WCAG 2.2. It has no dependencies and runs anywhere there is a DOM, with a median audit of 53 ms in AccessLint's February 2026 benchmark. Rocket Validator runs it on every page it crawls, on its own or alongside Axe Core.
AccessLint Core checks a rendered page against rules covering WCAG 2.2 Level A and AA, plus a set of best-practice checks that go beyond the standard — heading order, landmark structure, list semantics and skip links.
Rocket Validator publishes a remediation guide for every rule in the AccessLint 0.17 ruleset — 95 in total.
The engine has no runtime dependencies. It runs in browsers, in headless browsers, and in server-side DOM implementations like happy-dom and jsdom — including its colour-contrast checks, which most engines cannot evaluate outside a real browser.
It is MIT licensed, so you can read the source of every rule and see exactly what it tests. Results are classified by impact — critical, serious, moderate or minor — matching how Rocket Validator groups them in your reports.
Built for speed
AccessLint's published benchmark ran the engine against 5,000 sites from the Chrome UX Report and recorded a median audit of 53 ms. That figure is AccessLint's own measurement, taken in February 2026, not ours — and it predates the 0.17 release by several versions.
Speed matters more on a crawl than it does on a single page. When you are checking 5,000 pages, the engine either keeps up with the crawler or becomes the thing you wait on.
Rule coverage
Rocket Validator publishes a remediation guide for every rule in the AccessLint 0.17 ruleset, grouped by AccessLint's own taxonomy.
| Category | Rules |
|---|---|
| Labels and names category guides | 20 |
| Adaptable category guides | 13 |
| Aria category guides | 11 |
| Landmarks category guides | 10 |
| Navigable category guides | 8 |
| Text alternatives category guides | 8 |
| Distinguishable category guides | 7 |
| Keyboard accessible category guides | 7 |
| Enough time category guides | 4 |
| Readable category guides | 4 |
| Time based media category guides | 2 |
| Input assistance category guides | 1 |
| Total | 95 |
Rule IDs follow a category/name
pattern, so you will recognise them in your reports as
text-alternatives/img-alt
or distinguishable/color-contrast.
Standards covered
- WCAG 2.2 Level A and AA, with AAA colour contrast available as an option
- Best-practice checks beyond WCAG — heading order, landmark structure, list semantics, skip links
- Every rule maps to the WCAG success criteria that EN 301 549 incorporates
AccessLint maps its rules to WCAG success criteria, but unlike Axe Core it does not publish per-rule Section 508, EN 301 549 or RGAA tags. If your report has to map to a specific legal framework, Axe Core carries those tags directly.
What automated testing can — and cannot — catch
No engine, AccessLint or Axe included, finds every WCAG issue. What automation is good at is the mechanical, unambiguous checks:
The rest of the WCAG criteria require human judgment — things like evaluating whether alternative text is actually descriptive, whether focus order is logical, whether audio captions are accurate, or whether error messages are helpful. No automated tool can assess these reliably.
This is not a limitation unique to AccessLint or Rocket Validator — it is a fundamental characteristic of all automated accessibility testing. What Rocket Validator does is ensure you get the most out of the automated portion: running the complete rule set across every page on your site, so the issues that can be found automatically are found consistently and at scale.
How AccessLint Core compares with Axe Core
Rocket Validator also runs Axe Core, and the two engines can run on the same report. They were built independently and they do not have the same rules, so each issue is labelled with the engine that found it.
Detailed guides to help you fix what AccessLint finds
Every AccessLint rule has a detailed guide integrated directly into your report. These guides explain:
- What the rule checks and why it matters
- Which WCAG success criteria it relates to
- Code examples showing the issue and the fix
- Common scenarios where the issue appears
European Accessibility Act
The European Accessibility Act has applied since June 2025. If you sell digital products or services to customers in the EU, your site has to meet the accessibility criteria in EN 301 549, which incorporates WCAG Level A and AA.
Both engines check those criteria across every page Rocket Validator crawls. If your report has to show per-rule EN 301 549 tagging, run Axe Core, which carries those tags directly.
Rocket Validator is built and run from Spain, with servers in Paris, Amsterdam and Frankfurt. Your validation data stays in Europe.
Get started
The AccessLint Core engine is included on Pro, Agency and Enterprise plans, alongside Axe Core and W3C HTML validation.
Pro starts at €59/month with up to 50,000 checks, scheduled monitors, muting and device viewport emulation.
Technical details
| Engine | AccessLint Core 0.17 |
|---|---|
| Licence | MIT, source available |
| Rules | 95, mapped to WCAG 2.2 Level A and AA |
| Beyond WCAG | Heading order, landmark structure, list semantics, skip links |
| Dependencies | None |
| Size | 46 KB gzipped |
| Environments | Browsers, headless browsers, happy-dom, jsdom |
| Rule IDs |
category/name, for example
text-alternatives/img-alt
or distinguishable/color-contrast
|
| Impact levels | critical, serious, moderate, minor |
| Benchmark | 53 ms median across 5,000 Chrome UX Report sites — AccessLint's own measurement , February 2026, which predates 0.17 |
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