# Lighthouse Accessibility Score vs axe-core: What's the Difference?

Source: https://accessibilityscore.in/lighthouse-accessibility-vs-axe
Last reviewed: 2026-10-16 by the HalfAccessible accessibility team

Lighthouse, built into Chrome DevTools, gives every page an accessibility score out of 100. axe-core is the open-source engine behind many accessibility tools, including Lighthouse's accessibility audits. This guide explains how they relate, why their results differ, and what each is good for.

## Short answer
Lighthouse is Google's open-source page auditing tool; its accessibility category runs a selected set of axe-core checks and turns them into a score weighted by axe's user-impact ratings. axe-core is Deque's open-source rule engine itself. A Lighthouse score of 100 means no scored audit failed, not that the page is accessible.

## Key facts

- **Lighthouse:** Open-source tool from Google; runs in Chrome DevTools, from the command line or as a Node module
- **Engine under Lighthouse accessibility:** axe-core (Lighthouse pins axe-core 4.13.0)
- **How the Lighthouse score works:** Weighted average of pass/fail audits, weighted by axe user impact
- **Not in the score:** Manual audits and low-impact or best-practice audits
- **axe-core:** Open-source rule engine from Deque, licensed MPL-2.0
- **axe-core 4.13.0 rules:** 105 rules, 75 of them tagged with a WCAG level
- **axe result types:** Violations, passes, incomplete (needs review) and inapplicable

## How does Lighthouse calculate its accessibility score?

According to Chrome's documentation, the Lighthouse accessibility score is a weighted average of its accessibility audits. Each audit is pass or fail, and the weights are based on axe's user-impact assessments, so a failing high-impact audit costs more than a low-impact one. Manual audits and low-impact or best-practice audits do not affect the score.

Because each audit is simply pass or fail, one missing label and fifty missing labels cost the same. And because only automatable checks are scored, a page can score 100 while still being hard or impossible to use with a keyboard or screen reader.

## What does axe-core report that a Lighthouse score hides?

axe-core returns four kinds of results for each rule: violations, passes, incomplete and inapplicable. Incomplete results are checks that ran but could not decide, such as text contrast over a background image, and they need a person to review them. A single pass/fail score cannot represent them.

Running axe-core directly also lets you choose rule sets, for example only the rules tagged for WCAG 2.2 Level AA, and see every affected element for each rule.

## Why do Lighthouse, axe DevTools and AccessibilityScore.in give different results?

Even tools built on the same engine differ in what they run and how they count:

- Rule selection: Lighthouse runs a chosen set of axe checks as audits; other tools run more or fewer rules.
- Scoring: Lighthouse weights pass/fail audits by impact; AccessibilityScore.in starts at 100 and deducts 8, 4, 2 or 1 points for each failing critical, serious, moderate or minor rule.
- Extra rules: AccessibilityScore.in adds its own rules for visible focus, target size, accessible names, page language and page title.
- Page state: results depend on what has loaded, the viewport and whether a cookie banner or pop-up is open when the scan runs.
- Review items: AccessibilityScore.in lists axe's incomplete results as Needs review findings instead of dropping them.

## When should you use Lighthouse, axe-core or AccessibilityScore.in?

Use each where it fits:

- Lighthouse: a quick check while developing in Chrome, alongside performance and SEO audits.
- axe-core directly, or axe DevTools: automated accessibility tests in your test suite or CI, with rules you choose.
- AccessibilityScore.in: a shareable report for a public page or a whole site of up to 250 pages, with CSV and PDF exports and scheduled re-scans.
- All of them: as a first pass before manual keyboard and screen reader testing, never instead of it.

## Lighthouse vs axe-core vs AccessibilityScore.in

| Aspect | Lighthouse | axe-core | AccessibilityScore.in |
| --- | --- | --- | --- |
| What it is | Page auditing tool covering performance, accessibility, SEO and more | Accessibility rule engine (library) | Accessibility scanner and reporting service |
| Made by | Google | Deque | AccessibilityScore.in, powered by HalfAccessible |
| Accessibility rules | Selected axe-core checks | All axe-core rules you enable | axe-core plus custom rules |
| Score | Weighted average of pass/fail audits | None; raw results | 100 minus deductions per failing rule by severity |
| Needs-review items | Not part of the score | Returned as incomplete | Shown as Needs review findings |
| Scope | One page per run | Whatever you run it on | One page free; whole sites up to 250 pages |
| Cost | Free, open source | Free, open source (MPL-2.0) | One page free; $10 for 1,000 page credits |

## Common questions

### Does Lighthouse use axe-core?
Yes. Lighthouse's accessibility audits are powered by axe-core, and its scoring weights come from axe's user-impact ratings.

### Does a Lighthouse accessibility score of 100 mean my site is accessible?
No. It means none of the scored automated audits failed. Manual checks, such as keyboard use and meaningful alt text, are not part of the score.

### Is a Lighthouse accessibility score of 90 good?
It means most scored audits passed, but the remaining failures may still block some users, and unscored issues are not reflected. Fix the failing audits and test manually.

### Is axe-core free?
Yes. axe-core is open source under the MPL-2.0 licence. Deque also sells commercial products built on it.

### Why is my Lighthouse score different from my AccessibilityScore.in score?
They run different rule sets and score differently. Lighthouse weights pass/fail audits by impact; AccessibilityScore.in deducts points per failing rule by severity and adds its own rules.

### Which should I use in CI?
axe-core, through a test-framework integration, gives you the most control over rules and thresholds. Lighthouse CI is useful if you already track Lighthouse scores for performance.

## Sources

1. [Chrome for Developers: Lighthouse accessibility scoring](https://developer.chrome.com/docs/lighthouse/accessibility/scoring)
2. [Chrome for Developers: Introduction to Lighthouse](https://developer.chrome.com/docs/lighthouse/overview)
3. [Lighthouse on GitHub](https://github.com/GoogleChrome/lighthouse)
4. [axe-core on GitHub](https://github.com/dequelabs/axe-core)
5. [axe-core rule descriptions](https://github.com/dequelabs/axe-core/blob/develop/doc/rule-descriptions.md)

Run a free accessibility score: https://accessibilityscore.in