Contrast checker
Check text contrast against WCAG AA and AAA thresholds for normal and large text.
Opaque sRGB only: #RGB, #RRGGBB, rgb(0, 128, 255) or hsl(210, 100%, 50%). No alpha, named colors or percentages in RGB. Large text: at least 18 pt regular or 14 pt bold. This checks one color pair; it is not a full accessibility audit.
Runs in your browser. Inputs are not uploaded or saved.
How to use
Choose a mode, enter values or load the example, then copy or download your result.
Rules and worked example
Black on white has a contrast ratio of 21:1; identical colors have 1:1. Relative luminance is computed from linearized sRGB channels, then the ratio is (lighter + 0.05) ÷ (darker + 0.05).
Questions and answers
Which thresholds are tested?
WCAG AA requires 4.5:1 for normal text and 3:1 for large text. AAA requires 7:1 and 4.5:1 respectively. Pass/fail uses the unrounded ratio; the displayed ratio has two decimals. Large text means at least 18 pt regular or 14 pt bold. Real backgrounds, transparency, font weight and other accessibility criteria still need separate review.