QR Code Colors and Accessibility: Meeting WCAG Contrast for Scannable Codes

1. Two Audiences

A QR code must satisfy an optical sensor (contrast ratio for the decoder) and a human reader (WCAG 1.4.3 contrast ratio of 4.5:1 for surrounding text, and general visual clarity).

2. Sensor Contrast

Camera-based decoders require a luminance contrast of at least 4:1 between dark modules and the background. The ISO standard recommends 7:1 or better for reliable scanning.

3. Using Brand Colors Safely

Test candidate palettes with a luminance contrast calculator before printing: * Dark modules must be darker than the background in grayscale. * Avoid red on white: red appears bright in a grayscale conversion. * Blues, dark greens, dark purples, and charcoals generally work well.

4. Practical Steps

1. Pick your background (ideally off-white or light grey, not pure white on OLED screens, which can cause bloom). 2. Choose a foreground at least 4:1 contrast ratio. 3. Generate and scan the result on a real device in ambient indoor light.