Accessibility testing tools compared

These are the tools a person runs while testing one page: browser extensions, rule engines and screen readers. Each has a version you can run without buying anything. None of them can tell you a page meets WCAG 2.2 AA on its own, and the makers say so.

Looking for a platform that scans a whole site on a schedule? That is a different job, compared in website accessibility software and, for teams already quoted for an enterprise suite, in Siteimprove alternatives.

Fig. 1A checker lists its results down the side of the page, and one result row is ringed in orange

The verdict by use case

Best first scan for a site owner
WAVE
It draws each error and alert onto the page itself and shows you the alt text, so you see the problem where it sits.
Best for a developer fixing code
axe DevTools (free)
Its rules are tagged by criterion, it marks what it cannot decide, and the same engine runs in automated tests later.
Best for a guided keyboard and manual test
Accessibility Insights for Web
Its Tab stops helper and step-by-step Assessment cover the tests a scan cannot, and the report exports by criterion.

Side by side

Scroll sideways to see all vendors.

How the testing tools compare on what a page test needs
Requirement	WAVE	axe DevTools (free)	Accessibility Insights for Web	IBM Equal Access Checker	Lighthouse	Pa11y
Cites WCAG criteria by number	Yes	Yes	Yes	Yes	Not stated	Yes
Flags uncertain results for review	Yes	Yes	Yes	Yes	Not stated	Yes
Checks text contrast (1.4.3)	Yes	Yes	Yes	Yes	Yes	Not stated
Helps with the keyboard walk	Not stated	No	Yes	Yes	No	Not stated
Exports results to a file	Not stated	Not stated	Yes	Yes	Yes	Yes
Open-source rule engine	Not stated	Yes	Yes	Yes	Not stated	Yes
Extension for Chrome, Firefox and Edge	Yes	Yes	No	Yes	Not stated	No

The vendors

WAVE

What it is: WebAIM's free extension for Chrome, Firefox and Edge that draws icons for errors, alerts and structure onto the page itself.
Who it fits: An owner or editor who wants to see each problem where it sits, and to read the alt text and headings a screen reader gets.

Each finding names its WCAG 2.2 criterionYes
Alerts kept apart from errorsYes
Text contrast checkYes
Page never leaves your browserYes
Export to a fileNot stated

WAVE website

axe DevTools (free)

What it is: Deque's extension for Chrome, Firefox and Edge, running the open-source axe-core rules on one page at a time.
Who it fits: A developer fixing code, who wants the same rules later in automated tests; a paid Pro tier adds guided tests.

Rules tagged with WCAG criterion numbersYes
Uncertain results marked for manual reviewYes
Text contrast checkYes
Guided keyboard test in the free versionNo
Export to a file in the free versionNot stated

axe DevTools (free) website

Accessibility Insights for Web

What it is: Microsoft's open-source extension for Chrome and Edge: a quick FastPass plus a full Assessment against WCAG 2.1 AA.
Who it fits: Anyone with some HTML who wants a step-by-step manual test, keyboard included, and a report to keep.

Assessment report grouped by success criterionYes
Results it cannot decide sent to a personYes
Tab stops helper for the keyboard walkYes
Export as HTML or JSONYes
Runs in FirefoxNo

Accessibility Insights for Web website

IBM Equal Access Checker

What it is: IBM's open-source checker for Chrome, Firefox and Edge, inside the browser's developer tools.
Who it fits: A tester who wants violations and needs-review items split, a keyboard view and a report by requirement.

Results sorted by numbered requirementYes
Needs review kept apart from violationsYes
Text contrast checkYes
Keyboard checking viewYes
ReportsYes

IBM Equal Access Checker website

Lighthouse

What it is: Google's page audit built into Chrome DevTools, with an accessibility score beside performance and SEO.
Who it fits: A quick look in Chrome with nothing to install, read as a first pass and never as a verdict.

Each audit names a WCAG criterionNot stated
Text contrast auditYes
Keyboard items left for you to check by handYes
Manual checks count toward the scoreNo
Report saved as JSONYes

Lighthouse website

Pa11y

What it is: A free, open-source command-line checker on Node.js that runs HTML_CodeSniffer or axe rules on any URL.
Who it fits: A developer who wants a list of pages checked from the terminal or on every deploy.

Issue codes carry the WCAG criterionYes
Warnings and notices apart from errorsYes
Keyboard testNot stated
CSV, JSON or HTML outputYes
Needs no command lineNo

Pa11y website

What no automated checker can catch

Every tool in the table reads the code of the page in front of it. That is why each one can say an image has no alt attribute, and none can say whether the alt text is right. The gap shows most on the criteria below. Our alt text check takes the other half for one image at a time: you say what the image does, and it tests the alt text against that job.

Scroll sideways to see all columns.

What an automated checker can flag, and what still needs a person
Success criterion	A checker can flag	Only a person can judge
1.1.1 Non-text Content	An image with no alt attribute at all.	Whether the alt text says what the image is for. WebAIM says plainly that WAVE cannot judge this, so it shows you the text instead.
1.4.3 Contrast (Minimum)	Text on a flat background colour, measured against 4.5:1 and 3:1.	Text over a photo, a gradient or a see-through layer. Both Microsoft and WebAIM name these as cases their checks cannot settle.
2.1.1 Keyboard	A tabindex above 0, a common cause of a jumbled order.	Whether every menu, button, form and pop-up can be reached and worked with Tab, Enter, Space and the arrow keys.
2.1.2 No Keyboard Trap	Nothing reliable. Lighthouse lists trapped focus as a manual check.	Whether focus can leave every widget, chat window and embedded video by keyboard alone.
2.4.3 Focus Order	Accessibility Insights can draw the tab stops on the page.	Whether that order follows the meaning of the page. Lighthouse leaves this one to you.
2.4.7 Focus Visible	Little. The ring is a visual result of your styles.	Whether you can see where focus is at every stop, on every background.
1.2.2 Captions (Prerecorded)	A video element with no captions track.	Whether the captions are accurate, complete and in time with the speech.
4.1.2 Name, Role, Value	A button or link with no accessible name.	Whether a custom menu, tab set or slider announces what it is and its state when a screen reader reaches it.

What the tool makers say themselves

WebAIM: “WAVE cannot tell you if your web content is accessible. Only a human can determine true accessibility.”

Microsoft, on its own FastPass: “most accessibility problems can be identified only through manual testing and Automated checks only provide partial coverage to WCAG success criteria.”

W3C: “Web accessibility evaluation tools can not determine accessibility, they can only assist in doing so.”

The Justice Department says automated checkers “need to be used carefully”, that a clean report does not mean a site is accessible, and that they should be paired with a manual check.

Some vendors publish their own estimate of the share of issues automation finds. Each study counts in its own way, so we do not repeat a figure here. The safe reading is the one the makers give: a checker finds part of the problems, and a person finds the rest.

A clean report is not a pass

WebAIM writes that the absence of errors in WAVE does not mean a page is accessible or compliant. A Lighthouse accessibility score is a weighted average of automated audits that each pass or fail, and Google says its manual audits do not affect the score. A score of 100 means every automated audit passed, nothing more.

Screen readers and a colour picker

The other half of testing needs no rule engine. Three free tools cover it on a normal office computer. Our guide to screen reader testing for owners walks through a first session, and the contrast check runs the WCAG formula on any two colours you pick.

NVDA

NV Access, Windows

A free, open-source screen reader. Listen for a page title, headings in order, links that make sense out of context and a label on every field.

NVDA on its maker's site

VoiceOver

Apple, Mac (built in)

The screen reader built into macOS; Command-F5 turns it on and off. Its rotor jumps straight to a heading or a link, the quickest test of a page's structure.

VoiceOver on its maker's site

Colour Contrast Analyser

TPGi (Vispero), Windows and Mac

A free colour picker that reads the two colours from anywhere on screen and gives the ratio against WCAG 2.0, 2.1 and 2.2, with a colour blindness simulator.

Colour Contrast Analyser on its maker's site

Pick a kit for your setup

Which checkers you can run depends on your browser, and which screen reader depends on your computer. Choose yours and copy or print the list.

Pick your setup. The kit below changes as you choose. Pre-set to a Windows owner in Chrome.

Your computer

WindowsMac

Your browser

ChromeEdgeFirefoxSafari

Who runs the tests

I run the siteI write the code

Your kit: 4 tools

WAVEShows each error and alert on the page itself, and nothing is sent to WebAIM's server.
Accessibility Insights for WebIts Tab stops helper and Assessment walk you through the keyboard and manual tests.
NVDAA free, open-source screen reader for Windows. Listen to headings, links and form labels.
Colour Contrast AnalyserA free colour picker for Windows and Mac, for text over photos and gradients that checkers skip.

A routine for testing one page

Run it on your home page first, then on the page that earns money: the booking form, the cart, the quote request.

Run WAVE and fix the red errors first. Then read the alerts one by one; many are fine, some are not.
Run a second engine, axe DevTools or IBM's checker. The rule sets differ, and WAVE checks hidden content on purpose, so the two lists will not match. Fix what both agree on before you argue with either.
Put the mouse away and walk the page with Tab, Shift and Tab, Enter, Space and the arrow keys. The focus order checklist keeps the walk honest.
Zoom the browser to 200 percent. Criterion 1.4.4 Resize Text asks that text resize that far without losing content or function.
Check any text over a photo or gradient with the colour picker, since the checkers pass over it.
Turn on NVDA or VoiceOver and listen to the page title, the headings, the links, the form labels and the buttons.
Write down each problem against its criterion number in the WCAG 2.2 AA checklist. When the list is long, or the page takes payments, a manual audit by a specialist is the next step.

How we compared

Vendor pages read on October 22, 2026

We chose tools a person runs on one page while testing, each with a version that costs nothing to run, and read every status on the maker's own pages. A status we could not read there says “Not stated”. Free versions are compared; paid tiers are named only where the maker describes them.

Site-wide scanning platforms are compared on their own page. W3C keeps a longer list of evaluation tools; providers submit the entries and W3C does not verify them. It is one of the official lists in our directory.

Verdicts are editorial: no vendor can buy a verdict position or displace another vendor.

No overlay widget is listed. By an overlay we mean a third-party widget or toolbar script sold as making a site conform without changing its source. In April 2025 the FTC approved a final order that bars one overlay vendor from claiming, without evidence to support it, that its automated products can make any website WCAG-compliant. Read the FTC's announcement of the order.

Nothing here is legal advice. For a specific case, ask a lawyer.

Questions

Is a free checker enough to meet WCAG 2.1 AA?

No tool on this page claims that. A checker finds part of the problems; the keyboard walk, the screen reader pass and a judgement on alt text, captions and focus order find the rest. Use both halves, then record the result against each criterion.

Should I use WAVE or axe DevTools?

Both, on the same page. They run different rule sets and WAVE checks hidden content on purpose, so their lists differ. WAVE shows its findings on the page, which suits a reader who is not a developer; axe lists them beside the code, which suits one who is.

Does a Lighthouse score of 100 mean my site is accessible?

No. Google describes the score as a weighted average of automated audits that each pass or fail, and its manual audits do not affect the score. A 100 means every automated audit passed.

When is a paid tool worth it?

When a team tests often. Deque's paid Pro tier adds guided tests and reporting to the free extension. For one small site, the free tools plus a screen reader cover the testing; the cost is your time.

Can an overlay widget replace these tools?

No. An overlay is a third-party widget or toolbar script sold as making a site conform without changing its source, so it neither tests nor fixes your code. Our guide to accessibility overlays explains what they do and what the FTC said, and if you are taking one off, what to use instead of accessiBe pairs these tools with audit services.

Why do two tools give different results on the same page?

Each maker writes its own rules and decides what counts as an error, an alert or a needs-review item. A disagreement is a prompt to look at that element yourself, not a sign that one tool is broken.