Multi-Engine Comparison
Run axe-core, Pa11y, and Lighthouse simultaneously and compare their results side by side.
Why use multiple engines?
No single accessibility engine catches every issue. Each engine has different rule sets, detection methods, and coverage areas. Running all three together gives you the most comprehensive accessibility picture — and helps you identify issues that only one engine detects.
The three engines
axe-core
Developed by Deque Systems. The industry standard for automated accessibility testing. Known for zero false positives — every issue it reports is a real violation.
Pa11y
Open-source accessibility testing tool using HTML_CodeSniffer. Provides broad WCAG coverage and catches issues that axe-core may miss, particularly around HTML structure and ARIA usage.
Lighthouse
Google's open-source auditing tool. Combines accessibility testing with performance, SEO, and best practices audits. Uses axe-core internally but adds additional checks and scoring.
Engine comparison
| Feature | axe-core | Pa11y | Lighthouse |
|---|---|---|---|
| False positives | None | Low | Low |
| WCAG 2.2 support | ✅ | ✅ | ✅ |
| Section 508 | ✅ | ✅ | ❌ |
| EN 301 549 | ✅ | ✅ | ❌ |
| Performance audit | ❌ | ❌ | ✅ |
| Accessibility score | ❌ | ❌ | ✅ |
| AAA rules | ❌ | ✅ | ❌ |
| Speed | Fast | Medium | Slow |
How to run a multi-engine audit
- 1
Open the audit form
Click New Audit from the dashboard.
- 2
Enter the URL
Enter the URL of the page to audit.
- 3
Select all three engines
Check axe-core, Pa11y, and Lighthouse in the engine selection area.
- 4
Click Run Audit
All three engines run in sequence. Results are merged and deduplicated in the Results Panel.
Reading multi-engine results
In the Results Panel, each violation shows which engine(s) detected it:
Detected by all engines
High confidence — definitely a real issue. Prioritize these fixes first.
Detected by one engine only
May be engine-specific. Review manually to confirm it is a real issue before fixing.
Lighthouse score
Lighthouse provides an overall accessibility score (0–100). Aim for 90+ for good accessibility.
💡 Recommendation
For enterprise audits and VPAT generation, always run all three engines. This gives you the most comprehensive coverage and the strongest evidence of accessibility compliance.