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Image Contrast Checker

Measure WCAG contrast ratios inside a photo and between any two colours you sample from it.

Measure the contrast

Darkest to lightest region: —
Colour A to colour B: —
WCAG verdict: —
Click the preview to sample a colour. The relative luminance follows the WCAG 2.1 definition.

How to use the Image Contrast Checker

  1. Load the photo whose contrast you want to measure.
  2. Sample two colours by clicking the preview, or use the darkest and lightest regions.
  3. Read the WCAG ratios and the AA and AAA pass or fail verdict.

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Frequently Asked Questions

Common questions about the free online image contrast checker.

It is the brightness difference between two colours expressed as a number from 1 to 21, where 21 is black against white.
Each colour is converted to relative luminance with the WCAG formula, and the ratio compares the lighter and darker values.
WCAG AA needs a ratio of at least 4.5 to 1 for normal text, and AAA needs at least 7 to 1 for comfortable reading.
Click the pick colour A or pick colour B button first, then click anywhere on the preview to read that exact pixel.
It compares the darkest and the lightest pixel in the whole photo, which shows the maximum contrast the image already contains.
No. The image is read locally and every pixel is examined in your browser, so nothing is sent anywhere.
Many photos never contain both pure black and pure white, so the highest possible ratio in the image may be well below 21 to 1.
Yes for images of text and interface mockups. For live text use the calculated ratio and remember that font size changes the threshold.
Yes. Tap the pick buttons and then tap the preview to sample colours on any modern mobile browser.

Last updated: October 10, 2026