Methodology.
The score, the inputs, the weights, the math. Published because the alternative, proprietary opaque scoring, is the pattern that earned an overlay vendor a $1M FTC fine in January 2025.
What the score represents.
The Heuristic Risk Indicator is a 0-100 number summarizing how many common WCAG violation patterns a website has. It is not a WCAG compliance score, and it is not a legal assessment of any kind.
We call it “heuristic” deliberately. It is not a statistical model trained on a labelled dataset of court outcomes. It is a rule-based ranking informed by (1) axe-core's own impact ratings, (2) public accessibility audit data we have collected and reviewed, and (3) published reporting on common accessibility issues (Seyfarth Shaw ADA reports, WebAIM surveys).
The math is below. The weights are below. Both are versioned and bumped when they change, so a score generated last quarter can be traced back to the exact methodology that produced it.
How the score is calculated.
The score takes a weighted sum of every violation, applies a log-scaling curve so individual violations matter less as totals grow, and clamps to a 0-100 range.
score = clamp(0, 100, round(log10(sum + 1) * 20))
where sum = Σ over violations of
(weight[rule_id] × impact_multiplier[severity])
weight[rule_id] ∈ [0..100] // see table below
impact_multiplier = {
critical: 1.5,
serious: 1.2,
moderate: 1.0,
minor: 0.7
}Log scaling keeps the score on a bounded 0-100 range while preserving meaningful differences between low-violation sites (where each violation matters) and high-volume sites (where adding the 100th violation should not register the same impact as adding the 1st).
Per-rule weights.
Higher weight means the rule appears more often in demand letters and/or has higher axe-core impact. Rules not listed default to a weight of 10.
| axe-core rule | Weight |
|---|---|
| image-alt | 89 |
| input-image-alt | 85 |
| label | 72 |
| color-contrast | 68 |
| keyboard | 61 |
| bypass | 55 |
| link-name | 48 |
| button-name | 45 |
| html-has-lang | 32 |
| document-title | 28 |
| tabindex | 25 |
| frame-title | 22 |
| aria-required-attr | 18 |
Severity multipliers.
Each violation is weighted again by its axe-core impact rating.
critical
× 1.5
serious
× 1.2
moderate
× 1
minor
× 0.7
Requesting the underlying data.
We share the redacted case samples that informed these weights on request. Email contact@axeazy.com with your bar number; we respond within two business days.