Comparison
Percelia vs. axe DevTools & automated testing tools
2 min read
In short
axe DevTools, Lighthouse and WAVE are strong developer tools that check deterministic rules. Percelia uses the same axe-core engine but adds five more analysis layers, human review and a defensible conformance statement. Automated rules alone cannot decide every WCAG A/AA criterion.
axe DevTools by Deque is an excellent testing tool for developers, and we use the underlying axe-core engine in Percelia ourselves. So the comparison is not „rule tool or Percelia“, but „rule tool alone or rule tool as part of a full audit“.
Testing tool vs. Percelia at a glance
| axe DevTools / testing tool | Percelia | |
|---|---|---|
| What it is | A developer testing tool or browser extension | A full audit service |
| Coverage | Deterministic rules | Six layers: rules, keyboard, AI judgment, adaptation/reflow, accessibility tree, dynamic behaviour |
| Rule engine | axe-core | axe-core plus five layers of our own (we build on it) |
| Human review | No | Yes, for the ambiguous cases |
| Output | A list of rule violations in the browser | A documented report with code fixes and VPAT / EN 301 549 |
| Legal evidence | No | A defensible conformance statement with sign-off |
| Typical use | Developers in the IDE while coding | Organisations proving compliance |
| Ongoing control | Re-run manually | Continuous monitoring plus a CI gate against regressions |
Where automated tools reach their limits
No automated tool can reliably decide every WCAG A/AA criterion. Whether an alt text fits in substance, whether focus and reading order make sense, whether a checkout works with the keyboard alone, or whether contrast over an image is still legible cannot be settled by rules alone. These very cases are the most common reason a page is non-conformant despite a „green“ tool result.
What Percelia adds
Percelia starts with the same deterministic rules (axe-core plus our own contrast check) and adds keyboard and interaction testing, AI-assisted judgment over screenshot and DOM, adaptation/reflow tests, accessibility-tree analysis and dynamic form behaviour. Every finding carries a confidence; anything ambiguous goes to human review. Which WCAG criteria can be automated, and how far, is shown in our WCAG reference.
When to use which
Catching rule violations quickly while coding is what a testing tool is for, and the same engine runs as our layer one. Using Percelia therefore does not cost you that check, it adds five more layers, human sign-off and the documented conformance statement on top. Defensible BFSG evidence needs exactly that. What a full audit costs is in the guide on audit costs.
Frequently asked questions
- Is axe DevTools enough for BFSG evidence?
- No. axe DevTools finds deterministic rule violations, but automated rules cannot decide every WCAG A/AA criterion. Defensible evidence needs additional testing layers and human assessment.
- Does Percelia use axe?
- Yes. Percelia uses the axe-core engine in its first analysis layer and adds five more layers plus human review. We build on axe rather than replace it.
- What is the difference between a testing tool and an audit?
- A testing tool checks automated rules and reports violations. An audit assesses the whole page across several layers, brings in human judgment and results in a documented, defensible conformance statement.
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