Contrast checkerValidators

Color contrast checker. WCAG ratio and the fix.

Pick a text colour and a background. You get the contrast ratio, pass or fail for WCAG AA and AAA at normal and large text sizes and for UI parts, a live preview, and the closest text colour that passes when yours does not.

Cost to you

Free

Runs in your browser. No signup, no API call, no limit per hour.

browser
runs in
none
API calls
none
account

Use it now

Use the Color contrast checker here

It runs in your browser. Nothing you type is sent anywhere, there is no signup and no limit.

Loading the tool.

Run it from your agent

Copy one prompt, give it to your agent.

Fill in the placeholder, paste it, and the agent runs the same job with current data on your looot account and shows the cost.

  • You give it: a text colour and a background colour, as hex or rgb.
  • Billed per call, nothing while your agent is idle.
  • The agent shows the price before it calls.
Prompt: Color contrast checker
Use looot to audit the colours of a landing page. 1. Set up https://looot.ai/skill.md. 2. Search the catalog for an endpoint that returns a page's HTML or a screenshot and check its price before you call. 3. Fetch [URL]. 4. List the main text and background colour pairs. 5. Work out the WCAG contrast ratio of each and flag every pair under 4.5 to 1 for body text.

Give this to your agent
Setup command
set up looot - https://looot.ai/skill.md

What comes back

What your agent gets from color contrast checker

Field names as the providers return them. The exact set varies by endpoint, and your agent reads it from the catalog.

  • contrast ratio
  • AA and AAA pass or fail for normal and large text
  • UI component check
  • nearest passing text colour

Use it for

What people do with color contrast checker

  • Pass an audit

    Check every text and background pair before an accessibility review.

  • Pick brand colours

    Find the darkest shade of a brand colour that still reads on white.

  • Check dark mode

    Test grey text on a dark surface, where contrast often drops.

  • Fix a failing pair

    Use the suggested colour to pass AA with the smallest change.

Set up once

Three steps. Your agent does the rest.

Keep going

More free tools

FAQ

Questions about color contrast checker

For AA, 4.5 to 1 for normal text and 3 to 1 for large text and for UI parts such as input borders and icons. For AAA, 7 to 1 for normal text and 4.5 to 1 for large text.

At least 18 point, which is 24 CSS pixels, or 14 point bold, which is about 18.66 pixels. Most body copy is normal text.

Each colour's relative luminance is computed from its sRGB channels. The ratio is (lighter plus 0.05) divided by (darker plus 0.05). It runs from 1 to 1 for the same colour to 21 to 1 for black on white.

WCAG compares the exact ratio with the threshold, without rounding. The page cuts the ratio to two decimals instead of rounding, so a failing pair never shows as 4.50.

The page mixes your text colour toward black or white, whichever adds contrast, in 1 percent steps, and stops at the first mix that passes. That keeps the hue close to yours.

No. The alpha digits of an 8 digit hex code are ignored. Blend the colour with its background first and check the result.

No. It uses the WCAG 2 formula, the one in WCAG 2.2 and in most accessibility laws today.
For agents
tool
Color contrast checker
category
Validators
input
A text colour and a background colour, as hex or rgb
output
contrast ratio, AA and AAA pass or fail for normal and large text, UI component check, nearest passing text colour
price
per call, read live from the catalog on the web page
web tool
runs in the visitor's browser, no API call, free and unlimited
schedule
on demand
setup
https://looot.ai/skill.md
llms.txt
https://looot.ai/llms.txt
updated
2026-10-14
markdown /free-tools/color-contrast-checker.md

Run color contrast checker from your own agent.

Start your workspace, top up, and paste the prompt into the agent you already use. It runs the job with live data and shows the cost first.

Start your workspace See all free tools