CTA Button Color Contrast Checker (WCAG AA Compliance)
White text on vibrant primary call-to-action button.
WCAG 2.1 Contrast & APCA Checker
Normal body text (16px, 400 weight). If this text is difficult to read against the background, your visitors will experience cognitive fatigue and bounce within seconds.
Accessibility Verdict & Guidance:
- Meets standard legal requirements for body text (4.5:1) and buttons.
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Methodology & Grounded Benchmarks
What are the official WCAG 2.1 contrast thresholds?
WCAG Level AA requires a contrast ratio of at least 4.5:1 for normal body text and 3.0:1 for large text (≥18pt or 14pt bold). Level AAA requires 7.0:1 for normal text and 4.5:1 for large text. UI components and graphical boundaries require 3.0:1.
How is relative luminance calculated?
According to W3C specs, each sRGB color component (R, G, B) is linearized: values ≤ 0.04045 are divided by 12.92; otherwise, ((value + 0.055) / 1.055)^2.4. Luminance L is computed as 0.2126*R + 0.7152*G + 0.0722*B. The contrast ratio is (L1 + 0.05) / (L2 + 0.05).