Nothing is more frustrating than a beautiful print campaign with a QR code that doesn't work. Scannability depends on three factors: Size, Contrast, and Resolution.
The Size Rule of Thumb
The scan distance to size ratio should be roughly 10:1. If someone is scanning from 1 meter away, the code should be 10cm wide. For business cards (held close), 2cm x 2cm is the absolute minimum.
Contrast and Colors
Always use a dark foreground and a light background. While custom colors are possible, inverted codes (white pattern on dark background) are often difficult for older smartphone cameras to recognize.
File Formats Matter
Never use a low-resolution JPG for printing. Always use SVG or PDF formats. These vector files can be scaled to any size without losing clarity, ensuring your QR code is crisp and scannable even on a billboard.