Short answer: A website accessibility checker scans a page for barriers that software can find, like low contrast or images without a text alternative. It can’t see everything. The W3C says human judgement is required, so run a free checker first and then review the page yourself.
What an accessibility checker does
The W3C describes software programs and online services that help you identify accessibility barriers. They can run fully automated checks and help you with a manual review.
It also sets the limits. Tools cannot check all accessibility aspects automatically, some checks require manual intervention, and tools can sometimes produce false or misleading results.
How Lighthouse scores accessibility
Lighthouse, the tool PageSpeed Insights runs, gives each page an accessibility score. Google’s Chrome documentation says it is a weighted average of all accessibility audits, with weights based on axe user impact assessments.
Each audit is pass or fail, with no points for passing part of it. Manual audits don’t affect the score, so a high number can sit next to checks nobody has done.
Our PageSpeed Insights guide explains the other scores in the same report.
What a tool finds and what needs a person
| Check | What a tool can tell you | What a person still has to judge |
|---|---|---|
| Color contrast | Which text falls below the contrast ratio | Text over photos and moving parts |
| Images | Which images have no text alternative | Whether the text says what the image means |
| Headings and title | Whether they exist and follow an order | Whether they describe the content |
| Forms | Which fields have no label | Whether the labels and errors are clear |
| Keyboard | Some focus and order problems | Whether every action works with the keyboard alone |
| Text size | Whether the page blocks zooming | Whether the page still works with larger text |
Built from the W3C’s Easy Checks and its page on selecting evaluation tools, read November 3, 2026.
How to check your site
- Run Lighthouse or PageSpeed Insights on your main pages, on mobile and on desktop.
- Go to the list of failed audits under the score and fix each one.
- Open the manual checks the report leaves for you and go through them.
- Do the W3C Easy Checks: page title, image text, headings, contrast, text size, keyboard, forms and media.
- Move through each page with the Tab key and make sure you can always see where you are.
- Zoom the text in your browser and check that nothing gets cut off or overlaps.
- Run the checker again after every design change.
Our color contrast checker guide covers the contrast step in depth, and our ADA website compliance guide covers what the law asks of a business website.
What our own check found
On November 3, 2026, we ran Lighthouse’s accessibility audits through PageSpeed Insights on our home page and one guide, on mobile and desktop.
At 10:28 PM, both pages scored 100 on desktop with one failed audit. Our language links show EN and ES, but their accessible names were English and Español, which don’t contain the visible text. That audit carries a weight of 0, so it didn’t lower the score. We renamed the links EN, English and ES, Español at 10:29 PM.
The next run, at 10:30 PM, gave the home page 97 for a second failure: color contrast, an audit that does count toward the score. A “Scroll →” hint faded to 40% opacity in a loop, and Lighthouse measured its blue text at 2.25 to 1 against white. Nothing in the styles had changed since the first run, which passed contrast: the hint moves, so the result can change with the moment the tool measures it. At 10:31 PM we kept the motion and dropped the fade.
At 10:32 PM all four runs scored 100 with no failed audits. Each still listed 10 checks for a person to do.
Before you call your site checked
- Your main pages were tested on mobile and desktop.
- No audit fails, whatever the score says.
- The manual checks of the report are done.
- Every action works with the keyboard alone.
- Text stays readable when zoomed in.
- The test runs again after each design change.
RememberA checker finds part of the problems: read the failed audits, then check the rest yourself.
If you want a site that passes these checks from the start, our web design service can build it with you.
Quick answers about accessibility checkers
Does a score of 100 mean my site is accessible?
No. The W3C says tools cannot check all accessibility aspects automatically and that human judgement is required. On our own site, Lighthouse scored 100 while an audit with no weight in the score was failing, and every run left 10 checks for a person to do.
How is the Lighthouse accessibility score calculated?
Google’s Chrome documentation says it is a weighted average of all accessibility audits, with weights based on axe user impact assessments. Each audit is pass or fail, and a page doesn’t get points for partially passing one.
Can a checker show that my site meets the ADA?
Not on its own. A checker finds some barriers fast, but the W3C notes that tools can produce false or misleading results and that some checks cannot be automated. Use it as a first pass, then review the page yourself.
What should I check by hand?
The W3C Easy Checks start with the page title, alt text for images, headings and color contrast. Then they cover resizing the text, keyboard access with a visible focus, form labels and errors, and alternatives for audio and video.
Which free accessibility checker should I use?
PageSpeed Insights is a free option: it runs the Lighthouse accessibility audits, the ones behind our own case. The W3C notes that development teams may gain from using a combination of tools, so pair it with a manual review of your main pages.
Sources
Read on November 3, 2026. W3C Web Accessibility Initiative: Selecting Web Accessibility Evaluation Tools and Easy Checks. Chrome for Developers: Lighthouse accessibility score. Our own case: PageSpeed Insights accessibility runs on our home page and one guide, mobile and desktop, November 3, 2026.