Printing QR Codes

Print rules for reliable QR scans: minimum 0.8 in x 0.8 in (about 2 cm x 2 cm) on wall posters, 0.4 in x 0.4 in (1 cm x 1 cm) on business cards. For large-format prints, a useful rule of thumb is 0.4 in (1 cm) of QR size per 33 ft (10 m) of expected scan distance.

Contrast: dark code on light background always works. Light code on dark background usually works but is not guaranteed — many scanner apps are not optimized for inverted codes. Avoid inverse colors when reliability matters.

Quiet zone: the QR code needs a white (or high-contrast) border around it, roughly 4 modules wide. Without that margin, the camera cannot reliably detect the code's edges.