Website Accessibility Score Explained
Lighthouse catches roughly 30% of accessibility issues. Here's what the audit measures, what it doesn't, and how to fix the common red flags.
Table of contents
The Accessibility score in PageSpeed Insights / Lighthouse rates how well your site works for users with disabilities. It runs about 50 automated checks against the Web Content Accessibility Guidelines (WCAG) 2.1.
Here's what it measures, what it doesn't, and how to improve it.
The score ranges
| Score | Rating |
|---|---|
| 90–100 | Good |
| 50–89 | Needs improvement |
| 0–49 | Poor |
Unlike the Performance score, Accessibility is largely binary — each check either passes or fails. A few high-weight failures (like missing button labels or poor color contrast) can tank the score.
A realistic target is 95+. Most well-built sites can hit 100 on automated checks with an afternoon of work.
What Lighthouse actually checks
Color contrast
Background and foreground colors must meet WCAG contrast ratios:
- 4.5:1 for normal text
- 3:1 for large text (18px+ or 14px bold+)
This is the most common cause of imperfect scores. Light gray text on a white background, white text on a pastel button, low-contrast placeholder text — all fail.
Fix: Use a contrast checker (browser DevTools has one built in) and bump up the contrast until it passes.
Accessible names
Every interactive element needs a name a screen reader can announce:
<!-- ❌ No accessible name -->
<button><svg>...</svg></button>
<!-- ✅ Accessible name via aria-label -->
<button aria-label="Open menu"><svg>...</svg></button>
<!-- ✅ Or visible text -->
<button>Menu<svg>...</svg></button>
Common failures:
- Icon-only buttons with no
aria-label - Form inputs without
<label> - Links with only an icon and no text alternative
- Images used as buttons without
alt
Image alt text
<!-- ❌ Decorative or unlabeled -->
<img src="/photo.jpg">
<!-- ✅ Decorative (explicitly empty) -->
<img src="/decoration.svg" alt="">
<!-- ✅ Meaningful image -->
<img src="/chart.png" alt="Quarterly revenue chart showing 30% growth">
Every <img> needs an alt attribute. Use empty alt="" for purely decorative images.
Heading order
Headings should be in logical order: H1 → H2 → H3, no skipping levels.
<!-- ❌ Skips from H1 to H4 -->
<h1>Page Title</h1>
<h4>Subsection</h4>
<!-- ✅ Logical order -->
<h1>Page Title</h1>
<h2>Section</h2>
<h3>Subsection</h3>
ARIA usage
Lighthouse flags broken ARIA:
- ARIA attributes on the wrong roles
aria-labelledbyreferencing IDs that don't exist- Conflicting roles (e.g.
role="button"on a<button>)
If you're not sure how to use ARIA, default to native HTML elements — they have built-in accessibility.
Document structure
<html>must have alangattribute (e.g.<html lang="en">)<title>must exist- Lists must use
<ul>,<ol>, and<li>correctly - Tables need
<th>for headers
Form controls
- Inputs must have associated
<label>elements nameattribute should be present- Autocomplete attributes for known fields (
autocomplete="email", etc.)
Mobile and zoom
[user-scalable="no"]is forbidden — users must be able to zoom- Minimum font sizes for legibility
What Lighthouse does NOT check
Automated tools catch a known subset of issues. Lighthouse will not detect:
- Whether your alt text is meaningful — "image.jpg" passes the check
- Keyboard usability — can you tab through everything and reach all interactive elements?
- Focus management in dialogs, dropdowns, modals
- Screen reader experience — does it actually make sense when read aloud?
- Color independence — is information conveyed by color alone?
- Cognitive accessibility — readability, plain language, error tolerance
- Time-based content — captions, audio descriptions, transcripts
- Motion sensitivity —
prefers-reduced-motionrespected
Studies suggest automated tools catch 20–40% of accessibility issues. A 100 Lighthouse Accessibility score is necessary but not sufficient for an accessible site.
How to actually test for accessibility
- Run Lighthouse to catch the automated issues. Hit 100.
- Tab through your site with only the keyboard. Can you reach everything? Is focus visible?
- Use a screen reader for 30 minutes. macOS has VoiceOver built in (Cmd+F5). NVDA on Windows is free.
- Test with axe DevTools — catches more than Lighthouse.
- Get user feedback from people with disabilities. Nothing beats real usage.
Why bother?
Three reasons, in increasing order of impact:
- Legal risk. ADA lawsuits in the US have increased every year for the last decade. Settlements are routinely $5,000–50,000.
- SEO. Accessibility correlates with semantic HTML, which Google rewards. Many a11y fixes also improve SEO.
- Real users. Roughly 15% of the world has some form of disability. Inaccessible sites exclude them from your product.
Quick wins
If you're starting from a 60–80 score, these usually get you to 95+:
- Fix color contrast on your primary buttons and links.
- Add alt text to every meaningful image. Use
alt=""for decorative ones. - Add
aria-labelto icon-only buttons. - Wrap form inputs in
<label>or associate viafor=. - Add
lang="en"(or your site's language) to<html>.
Then re-run the audit. Most of those issues take a few minutes each.
The bottom line
A 100 Lighthouse Accessibility score is the start, not the finish. It means you've fixed the obvious automated issues. Real accessibility requires manual testing, semantic HTML, and a mindset that includes all users.
For a related deep-dive, see what PageSpeed Insights actually checks.
Frequently Asked Questions
Is a 100 Lighthouse Accessibility score actually accessible?+
Not necessarily. Lighthouse only catches automated issues — about 30% of accessibility problems. A 100 score means no automated red flags but doesn't replace manual testing with screen readers and keyboard navigation.
Why does my Accessibility score keep changing between audits?+
Some checks are weighted heavily — a single missing alt text on a key image, or insufficient color contrast on a primary button, can drop the score 5–10 points. Small DOM changes between runs can flip the result.
Is accessibility required by law?+
In many jurisdictions, yes. The ADA in the US, EAA in the EU, AODA in Ontario, and equivalent laws require digital accessibility. Inaccessible sites are also bad for SEO and exclude up to 15% of potential users.
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