Color Contrast Checker

How to use Color Contrast Checker

Three simple steps, with your content kept on your device.

Built for useful work

Fast, focused, and made to be clear on every screen.

What is a color contrast checker

A color contrast checker measures how clearly text stands out from its background by computing a contrast ratio from the two colors' relative luminance. The result is a number such as 4.6:1 that you can compare directly against accessibility standards.

Designers, developers, and content editors use a wcag contrast ratio calculator to catch text that is too faint to read comfortably — the most common accessibility failure on the web.

How WCAG contrast ratios work

The WCAG 2.x formula converts each color to linear RGB, calculates relative luminance, and divides the brighter luminance by the darker one. The tool applies this exact formula, so the numbers match the spec.

The result is not a guess: it is deterministic color math. Because everything runs locally, you can check contrast for client work, prototypes, and internal design systems without sending the colors anywhere.

AA and AAA requirements for text

WCAG AA requires at least 4.5:1 for normal text and 3:1 for large text. AAA raises the bar to 7:1 for normal text and 4.5:1 for large text. The tool reports separate verdicts for all four combinations.

The verdicts appear as clear pass or fail results for each level, so you can see at a glance whether a pair of colors is ready for production or needs adjustment.

Checking the contrast of two colors

Use the color pickers to choose a foreground and background, or paste values directly as shorthand HEX, full HEX, or rgb()/rgba(). Both inputs update live, so you can check contrast of two colors in seconds.

The compact report includes the ratio, all four verdicts, and the best achievable level, and a one-click download produces a text file you can attach to a design review or issue ticket.

A quick example: black on white scores 21:1 and passes every level, while light gray on white often falls below 3:1 and fails even the large-text requirement. Running both pairs through the checker in under a minute shows exactly where a design needs adjustment.

Transparency and alpha channels

Colors with an alpha channel are composited over the background before the ratio is computed, matching how they actually appear on screen. This handles the common case of tinted overlays and translucent buttons.

Without that compositing step, translucent colors would report misleadingly high ratios. The tool does the composite for you, so the verdict matches what a visitor with low vision will experience.

Why accessible text colors matter

Low-contrast text is hard to read for everyone and impossible for many people with low vision. Meeting WCAG contrast levels is a legal requirement in many jurisdictions and a practical one for reaching a wider audience.

Keeping accessible text colors in your workflow is easy when the check takes seconds: verify each pair as you design it, and ship interfaces that pass AA as the default rather than an afterthought.

Related color tools

Contrast checking fits into Valestiom's color toolkit. The Color Picker converts between HEX, RGB, HSL, and named colors, and the Image Color Extractor pulls dominant palettes out of a photo or design file.

Together they cover the full workflow: extract a palette from an image, confirm every text pair passes contrast, and export the exact values your team needs.

Frequently asked questions