What is WCAG contrast — AA and AAA
Text contrast in WCAG 2: relative luminance, the 4.5:1 and 7:1 thresholds, and an online check.
WCAG 2 measures contrast as the ratio of two relative luminances. For normal text AA is 4.5:1, AAA is 7:1. Large text (18pt, or 14pt bold) already passes AA at 3:1.
Luminance is computed in linear RGB, not by eyeballing a HEX. A brand orange on white often passes a large heading and fails a tiny caption.
The ToolsHelper picker shows the ratio and AA/AAA grade against white and pure black #000000, the same color as the On black card.
WCAG contrast is a ratio of the relative luminance of two colours. 4.5:1 is the usual AA bar for normal text, 3:1 for large text, and 7:1 for AAA. White on #ff7e15 fails normal text. The ratio is not a taste score: a design can look strong and still fail. This page defines the ratio. The colour tool computes it for the pair you pick.
FAQ
Do I need WCAG 3 already?
Web specs still quote WCAG 2.x thresholds. APCA from WCAG 3 has not replaced them in most briefs.
Is contrast to #111 the same as #000?
No. Measure against the background the text actually sits on.