Contrast Checker

Good to know

• Large text means roughly 24px, or 19px when it is bold. That is why it has its own thresholds: bigger shapes stay legible at a contrast that would fail for body text.
• The ratio runs from 1:1 for two identical colours to 21:1 for black on white, and it is symmetric — swapping text and background never changes it.
• The figure is computed on linear light rather than on the stored channel values, which is why a colour that looks midway between black and white scores nowhere near 10:1.
• Passing the ratio is a floor, not a finish line. Thin weights and small sizes can still be hard to read at exactly 4.5:1.