How to Create a QR Code That Actually Scans Every Time
A reliable QR code needs strong contrast between the code and its background, enough physical size relative to the scanning distance (roughly 1 inch of code per 10 feet of scan distance as a rough guide), a clear quiet zone (margin) around it, and testing on an actual phone camera before printing or publishing it anywhere.
A QR code that looks fine on a screen can fail completely once printed small on a flyer or displayed on a poorly lit sign — the difference almost always comes down to a handful of practical details.
Contrast and color matter more than design
Dark code on a light background (classic black on white) scans most reliably. Low-contrast color combinations, code printed over a busy image, or a light code on a dark background all increase the chance a scanner fails to lock onto the pattern, especially in poor lighting.
Size relative to scanning distance
A QR code needs to be large enough for a phone camera to resolve its fine detail at the distance it'll actually be scanned from. A code on a business card, scanned from a few inches away, can be small. A code on a poster meant to be scanned from several feet away needs to be proportionally larger — a common rough guideline is roughly 1 inch of code size for every 10 feet of expected scanning distance.
The quiet zone and final testing
QR codes need a clear margin (the "quiet zone") of blank space around them — cropping too tightly or placing other content directly adjacent to the code confuses scanners trying to locate its edges. Before finalizing anything for print or wide distribution, testing the actual code with a real phone camera, at the real size and in similar lighting to where it'll be used, catches problems no amount of on-screen review will reveal.