Contrast Ratio

A numerical measure of the difference in perceived brightness between two colors, expressed as a ratio ranging from 1:1 (no contrast) to 21:1 (maximum contrast, black on white). WCAG 2.2 requires a minimum contrast ratio of 4.5:1 for normal text and 3:1 for large text (Level AA), with enhanced requirements of 7:1 and 4.5:1 respectively at Level AAA. Sufficient contrast is essential for users with low vision, color vision deficiencies, or those viewing screens in challenging lighting conditions. The ratio is calculated using relative luminance values derived from the sRGB color space.