Lighthouse and Accessibility Checkers vs a UX Scan: What Each One Tells You
A green Lighthouse score feels like proof that your site is in good shape. Then a founder watches a first-time visitor land on the page and leave in ten seconds, and the score stops feeling like an answer.
Both statements can be true. Lighthouse and accessibility checkers measure technical quality. A UX scan reads what a visitor sees and judges whether it makes sense. This guide compares them, shows where each one stops, and gives a rule for choosing. Our Free UX Scan sits on the visitor side of this comparison, and we say plainly where the technical tools do better.
What each one is
Lighthouse is described by Google's Chrome team as an open-source, automated tool to help you improve the quality of web pages, with audits for performance, accessibility, SEO, and more. You can run it in Chrome DevTools, from the command line, or through a web interface. In DevTools, a report arrives after 30 to 60 seconds.
Automated accessibility checkers test pages against technical rules, such as whether images have alternative text, whether form fields have labels, and whether text has enough contrast. Lighthouse includes a set of these, and dedicated tools go deeper.
A UX scan loads a public page, reads the visible text and layout, and reports where a first-time visitor is likely to get stuck. Ours quotes the exact line behind each finding. The form on our site sends a written report by email, with up to 3 priority fixes. The connector returns a read of one public page: a one-line verdict, a score for each rubric area, and the strongest finding. It is limited to 6 scans an hour per network.
Side by side
| Dimension | Lighthouse | Accessibility checker | UX scan |
|---|---|---|---|
| Core question | Is the page fast, technically sound, and findable? | Does the code follow accessibility rules? | Can a stranger understand and act on this page? |
| Checks | Performance, accessibility, SEO, best practices | Labels, alt text, contrast, ARIA, structure | Message, call to action, trust, visual credibility |
| Output | Scores and failed audits | Lists of rule violations | Verdict, scores, quoted findings, a fix |
| Who acts on it | Developers | Developers and designers | Founders, marketers, designers |
| Sees behind a login | Yes, in DevTools | Depends on the tool | Public page only |
| Reads the wording | Leaves wording alone | Leaves wording alone | Yes |
| Reads trust and clarity | Leaves them alone | Leaves them alone | Yes |
| Strong at | Speed, structure, code hygiene | Catching mechanical accessibility errors | First impressions and the next step |
| Weak at | Meaning and persuasion | Full accessibility, which needs manual testing | Code quality, speed, and deep accessibility |
| What you need | A browser | The checker you choose | A public URL |
What Lighthouse and accessibility checkers do well
They check things people cannot see. Missing form labels, broken heading order, and images with no alternative text are invisible to a casual reader and matter to screen reader users. A tool finds them in seconds.
They are consistent. Each Lighthouse accessibility audit is pass or fail, and a page gets no points for partially passing. The score is a weighted average of all accessibility audits, so the same page gives the same answer.
They measure speed. Lighthouse reports load time. A scan of visible text reports the message, the next step, and the trust signals.
They flag contrast. The W3C asks for a contrast ratio of at least 4.5:1 for normal text and 3:1 for large text. A checker calculates that for every text and background pair.
Where they stop
A high score says little about accessibility
Automated tools have a ceiling. The UK Government Digital Service tested 13 automated accessibility tools against a page with 142 deliberately introduced barriers. The best tool found 40% of them, and the worst found 13%. Counting barriers that needed a human to confirm, the best tool reached 50%. The audit dates from 2018, and tools have changed since, so treat the numbers as an illustration of the pattern.
The UK Department for Work and Pensions accessibility manual draws the practical conclusion: automated testing is an easy way to find obvious errors, and it is not enough to guarantee accessibility. It adds that automated testing tools tend to scan one page at a time, whereas many WCAG success criteria need to be assessed across multiple pages.
Lighthouse is open about this in its own scoring notes: manual audits do not affect your score. A perfect score means the automated checks passed. The manual checks are still on the list.
They leave the message unread
Lighthouse can confirm that your headline is a proper heading. Whether that headline says what the product does is a separate question. It can confirm your button has an accessible name. Whether three buttons compete for the first click is a visitor question.
Those problems cost visitors in the first seconds. Nielsen Norman Group reports that users often leave pages in 10 to 20 seconds, and that you must clearly communicate your value proposition within 10 seconds. A page can pass every technical audit and still fail that test.
What a UX scan does well
It reads like a visitor. It judges whether the hero names the product, whether the next step is obvious, and whether the trust signals hold up. It quotes the line, so you can find the text on your page and fix it.
What a UX scan misses
A scan reads one public page at desktop width. Logins, load time, screen-reader testing, and an accessibility certification sit outside it. It flags low contrast as a visual issue, and that is a small part of accessibility work. When compliance matters, because of customers, procurement, or regulation, run the automated checks and arrange manual testing by people who specialize in it. Formal accessibility conformance needs that manual testing. Our post on what an automated scan catches and what it misses lists the limits.
Pick this if
Run Lighthouse or an accessibility checker first if:
- Your page feels slow or has never been checked for speed.
- You have developers who can act on technical findings today.
- You need a baseline for accessibility before a manual review.
- You are setting up a build pipeline and want regression checks.
Run a UX scan first if:
- Your technical scores are fine and visitors still leave.
- You are unsure the message is clear.
- You want fixes that a founder or marketer can make without a developer.
- You are about to launch and want a stranger's read.
Run both, in this order, if you can: the UX scan for message and next step, Lighthouse for speed and code hygiene, then a manual accessibility review for the conformance answer. Each one finds a different category of problem.
A simple routine
- Run Lighthouse on your homepage and your main landing page. Write down the failed audits.
- Run the scan on the same pages. The form sends a written report by email, and the connector returns a read of one public page.
- Sort the combined findings into two piles: copy and layout for the marketer or designer, code and performance for the developer.
- Fix the first screen first. Our 10-minute pre-launch check covers the basics. Manual accessibility testing is the step after the automated checks.
What a paid review adds
A Website UX Audit reviews your pages one by one for clarity, navigation, and conversion, with annotated findings and a prioritized fix list. A Product UX Audit covers key flows inside your app. Formal accessibility conformance still needs manual testing by people who specialize in it, alongside whatever the automated tools already flagged. Current offers are on our pricing page.
The short version
Lighthouse and accessibility checkers tell you whether the page is built well. A UX scan tells you whether a visitor will understand it. Use the technical tools for speed and structure, use the scan for message and next step, and bring in people for real accessibility.
Run the Free UX Scan on a page that already passes your technical checks. The form sends a written report by email, and the connector returns a read of one public page.
If you want a senior team to review the page with you, book a discovery call, or email us at ash@uxsignalstudio.com.