Question 1

What is a good WCAG contrast ratio?

Accepted Answer

WCAG AA requires a contrast ratio of at least 4.5:1 for normal text and 3:1 for large text (18pt or 14pt bold). WCAG AAA requires 7:1 for normal text and 4.5:1 for large text. Non-text UI components and graphical objects need at least 3:1.

Question 2

How is the contrast ratio calculated?

Accepted Answer

The ratio is calculated using the relative luminance of each color. The formula is (L1+0.05)/(L2+0.05) where L1 is the lighter and L2 is the darker relative luminance. Relative luminance accounts for how the human eye perceives different colors.

Question 3

What counts as large text for WCAG?

Accepted Answer

Large text is defined as at least 18pt (24px) regular, or 14pt (18.66px) bold. Large text has a lower contrast threshold (3:1 for AA, 4.5:1 for AAA) because larger characters are easier to read at lower contrast.

Question 4

Does this tool check AA or AAA compliance?

Accepted Answer

This tool checks both WCAG 2.1 AA and AAA levels simultaneously. For each color pair you test, you see pass or fail for normal text, large text, and UI components at both conformance levels.