A QR code that is not working can cost you leads and harm your brand. Most problems stem from a handful of recurring causes.
Design-related problems
Insufficient contrast is the number-one cause of scan failures. Maintain a minimum contrast ratio of 7:1. Never invert colours and avoid gradients on the modules.
Size and resolution issues
Minimum size equals scanning distance divided by ten. For a code scanned at one metre, plan for at least 10 cm per side. Ensure print resolution is at least 300 DPI.
Broken destination URL
Verify the URL is still live. Multiple redirects and expired SSL certificates are frequent causes. Test on at least three different devices before printing.
Quiet zone and padding
Every QR code requires a white border at least four modules wide. Without this space the reader cannot detect the code boundaries.