Color Contrast Ratio

Definitions

1. The relative luminance ratio between foreground text and its background, ranging from 1:1 (identical) to 21:1 (black on white). WCAG AA requires 4.5:1 for normal text and 3:1 for large text (18px+ bold or 24px+). Insufficient contrast makes text unreadable for users with low vision or in bright environments.

   In plain English: How easy text is to read based on the difference between the text color and background color.

   Example: "That light gray text on white has a 2.1:1 contrast ratio — bump it to at least 4.5:1 to pass WCAG AA."

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