How to Check Color Contrast for Accessibility (WCAG)

Contrast ratios run from 1:1 (identical colors, invisible) to 21:1 (pure black on pure white). WCAG sets four thresholds the checker tests against. For normal body text, AA requires a ratio of at least 4.5:1 and AAA requires 7:1. For large text — defined as 18.66px bold or 24px and larger — the bar is lower because bigger shapes are easier to read: AA needs 3:1 and AAA needs 4.5:1.

AA is the level most legal and organizational accessibility standards reference, so treat 4.5:1 for body text as your practical minimum. AAA is the stricter, enhanced target; hitting it is a nice goal for body copy but isn't always realistic with brand colors. The checker shows all four results at once so you can see exactly where a color pair lands.

The number at the top is your contrast ratio; the badges below translate it into pass or fail for each level. If you see a red Fail on AA for normal text, the two colors are too similar in lightness to be reliable for body copy.

The fastest fix is to push the two colors further apart in lightness rather than hue — darken the text or lighten the background (or vice versa). Small nudges matter: going from a mid-gray to a slightly darker gray can flip a Fail to a Pass. Use the live sample swatch to sanity-check that the result still looks the way you want. If a failing pair is only used at large sizes — a headline or a big button label — check the "Large text" row, since it may already pass AA there even when normal text doesn't.

Color values are harmless on their own, but the convenience of a tool that works instantly, without an account or upload step, is the real win. Tooldrop's contrast checker runs the WCAG algorithm right in your browser: you type colors, the ratio updates live, and nothing is sent to a server.

That means it's free with no sign-up and no usage limits, so you can check dozens of color pairs while iterating on a design system without hitting a paywall or a rate cap. Like most tools on Tooldrop, the processing happens on-device, which keeps it fast and keeps your work private.