Understanding axe-core rules and our scoring

What's axe-core?

axe-core is the open-source accessibility testing engine maintained by Deque. We use it as the foundation for automated testing because it's the most widely-used and well-maintained engine in the industry.

Our scoring formula

We compute a per-page score using:

• Severity weighting — Critical issues count for more than Minor ones.
• Issue density — 5 issues on a page with 1000 elements is better than 5 issues on a page with 50.
• WCAG level — Level A failures count for more than AAA.

The site-wide score is a weighted average across all crawled pages, with the homepage weighted higher than buried pages.

Why your score might fluctuate

• Content changes — a new page with issues drags the average.
• Rule updates — axe-core ships new rules every few months. We keep up; sometimes a new rule reveals issues we couldn't see before.
• JavaScript timing — dynamic content loaded after page render can show different issues run-to-run.

What axe-core can't catch

Roughly 30% of WCAG conformance requires human judgment — meaningful alt text, logical reading order, label clarity. See manual accessibility checks.