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Why isn't my QR code scanning?
Codes that scan perfectly on a monitor and fail on paper are the norm, not the exception. These are the causes, roughly in order of how often they're the actual problem.
1. It's too small for the distance
The most common cause by far. A code needs to be roughly one tenth of the distance it's scanned from: 30cm across for a three-metre scan, 2cm for arm's length. Codes sized for a business card do not work on a poster.
2. The quiet zone is crowded
QR codes need a blank margin around them — about four modules' worth — for the scanner to find the edges. Designers routinely crop it off or run a border right up to the code. It looks tidier and it breaks scanning.
3. Contrast is too low
Dark code on a light background, always. Pastel-on-white, white-on-brown kraft, and anything printed on a photograph all cut the contrast the camera needs. Coloured codes can work, but only with real contrast.
4. It's inverted
Light code on a dark background is technically readable and practically unreliable — plenty of phone cameras won't attempt it. If your brand demands a dark background, put the code in a light panel.
5. Gloss, varnish or lamination
Spot UV over a code, a gloss laminate, or a shiny sticker reflects light straight back into the lens. Matte finishes scan; gloss gambles. This is the classic 'works indoors, fails under the shop lights' cause.
6. The URL is too long
Longer text means more modules, which means a denser code that needs to be printed bigger to stay readable. A long URL with tracking parameters can double the density. Short links produce sparse, robust codes — one of the underrated practical benefits of a dynamic code.
7. It's printed across a fold or seam
Folds, box edges, spine creases and shrink-wrap seams distort the grid. Keep the code flat and whole.
8. The surface is curved
Bottles, cans, tubes and cups bend the code away from the camera. Keep codes small on tight curves, or place them on the flattest available panel.
9. Print quality or ink bleed
Low-DPI printing, ink spread on absorbent stock and toner streaks all blur module edges. Always scan a physical proof, not the PDF on screen.
10. Damage, and too little error correction
QR codes tolerate damage — up to about 30% at the highest error correction level. If codes live outdoors or get handled, generate them at high error correction so scratches and scuffs don't kill them. Codes made here use the highest level by default.
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Questions
My code works on screen but not when printed. Why?
Almost always size, finish or quiet zone. Screens are backlit, high contrast and perfectly flat — paper is none of those. Test the physical proof.
Does putting a logo in the middle break the code?
Not necessarily. Error correction is designed to tolerate obstruction, but a logo eats into that budget. Keep it small — under about 20% of the area — and always test the result.
Do coloured QR codes scan?
Yes, with sufficient contrast between the code and its background. Dark code on a light background is the safe pattern; light-on-dark is the risky one.
Related
- What size should a QR code be? — The rule is one tenth of the scanning distance, with a 2cm minimum. Sizes for business cards, flyers, posters, packaging and signage.
- Do QR codes expire? — QR codes don't expire on their own. What breaks is the link inside them, or the service running the redirect. Here's the difference.
- QR codes for product packaging — Boxes get printed months before the landing page is final. Put a dynamic QR code on the packaging and decide where it goes later.