Tool
What the Accessibility Color Checker does
Accessibility Color Checker: checks Contrast ratio, WCAG verdict and Nearest colour that passes AA from Text colour and Background colour.
From Text colour and Background colour, this tool derives Contrast ratio, WCAG verdict and Nearest colour that passes AA. You can nudge a single number and watch the effect straight away.
Most people who open the Accessibility Color Checker are anyone checking a colour for legibility. Contrast failures are the most common accessibility problem on the web, and the easiest to fix.
There is no account, no upload and no server round trip, because the page does the work itself.
The method, a field-by-field reference and a worked example built from the defaults are all on this page.
What do the Accessibility Color Checker fields mean?
The Accessibility Color Checker uses 2 inputs. Pre-filled inputs double as documentation: each one shows what a reasonable value looks like.
| Field | What to enter | Default |
|---|---|---|
| Text colour | optional | #1a1a1a |
| Background colour | optional | #ffffff |
How does the Accessibility Color Checker work?
Each output is derived from the inputs above in a single pass; there is no hidden state carried between runs, so the same inputs always give the same check.
The tool refuses to guess: if a value is missing or impossible, it says so.
What a typical run looks like
You provide: Text colour and Background colour
What happens: the file is read into memory by your browser, processed locally, and offered back as a download. It is never uploaded.
You get back: a download link for the new file and a short note on what changed.
Timing comes down to your own hardware, and the practical size limit is how much memory the browser will hand the tab.
How to use it
- Fill in Text colour.
- Type Background colour.
- Live output means you can search for a target value by nudging an input up and down.
- The panel reports Contrast ratio, WCAG verdict and Nearest colour that passes AA.
- Copy Link puts the current inputs in the URL, so bookmarking it brings the same numbers back.
What this tool does not do
- Conversions between colour spaces with different gamuts are approximate at the edges.
- Colours render differently across displays; the values are exact but the appearance is not guaranteed.
- There is no audit trail: if you need one, record the inputs alongside the output.
Frequently asked questions
Text colour and Background colour, nothing else. Every box already holds a working value, which means a single edit is enough to get a meaningful answer.
No. Your browser is doing the computing, so we could not see the values even if we wanted to.
No. There is no account, no usage cap and no trial period. The site is funded by advertising rather than by charging for the tools.
The logic is straightforward and testable; the worked example above uses the tool’s own defaults so you can verify it yourself.