Methodology
How we score
Every score on PillarScan is produced the same way, so numbers are comparable across pages, sites and time. This page explains the method so you can defend a number in a board meeting.
1. What we test
Each page is loaded in a real headless Chromium browser at 1280×800 and evaluated with axe-core, the open-source accessibility engine from Deque that underlies most professional tools. We run the rules tagged WCAG 2.0, 2.1 and 2.2 Level A and AA and report only violations (not "needs review" items). The DOJ rule's legal baseline is WCAG 2.1 AA; every 2.1 AA criterion is included.
2. Severity
| PillarScan | axe impact | Example |
|---|---|---|
| Critical | critical | Image without alt text, form field without a label |
| Major | serious | Insufficient color contrast, link with no accessible name |
| Minor | moderate, minor | Skipped heading level, content outside landmarks |
3. Page score (0–100)
For each failing rule on a page we add a penalty of weight × √min(elements, 16) with weights 10 (critical), 4 (major) and 1 (minor). The page score is 100 × e^(−penalty / 60). One critical rule on one element gives 85; three critical rules each on 16+ elements give 14. The curve never reaches zero, so every fix moves the number.
4. Site score and grade
The site score is a weighted average of page scores: the homepage counts three times, pages linked directly from it twice, everything else once. Grades: A ≥ 90, B ≥ 80, C ≥ 70, D ≥ 60, F below 60.
5. What a score does not mean
Automated testing detects roughly 30–57% of WCAG failures (depending on the study) and cannot judge the quality of alt text, caption accuracy, reading order or custom widget usability. An A means the common, machine-detectable barriers are gone and you have documented monitoring. It is not a certification or a legal opinion. Pages behind logins, PDFs and third-party portals are out of scope.
6. Versions
Every scan records the axe-core version and the scoring version used. When we upgrade axe-core, scores may shift slightly because new rules are added; the scan history shows the version next to each result.