Question 1

What is WCAG contrast ratio?

Accepted Answer

WCAG (Web Content Accessibility Guidelines) defines minimum contrast ratios to ensure text is readable. The ratio ranges from 1:1 (no contrast) to 21:1 (maximum, black on white).

Question 2

What are the WCAG AA and AAA requirements?

Accepted Answer

WCAG AA requires a contrast ratio of at least 4.5:1 for normal text and 3:1 for large text (18px bold or 24px regular). WCAG AAA requires 7:1 for normal text and 4.5:1 for large text.

Question 3

How is relative luminance calculated?

Accepted Answer

Each RGB channel is normalized to 0-1, then gamma-corrected: if the value is <= 0.03928, divide by 12.92; otherwise apply ((value + 0.055) / 1.055) ^ 2.4. Luminance = 0.2126*R + 0.7152*G + 0.0722*B.

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