“The QR doesn't work” is the vaguest complaint in retail — and in my bench of ~50 dead codes collected since 2024, 9 out of 10 came down to one of five things below. I have diagnosed dead codes on glass doors, crumpled receipts, sun-bleached boards and 300-character URLs shrunk to stamp size. Run this QR code not scanning checklist in order; most codes are fixed by step 2 without reprinting anything.
If you landed here with a dead code in hand — start at cause #1 below and work down. Full system: free QR code generator guide. Regenerate clean codes in the free QR code generator; verify what any code contains with the QR scanner.
The 5 causes, in order of likelihood
1 — Too small or too dense (fixes ~60% of cases)
A 200-character URL at 2 cm is a brick wall for budget cameras. Fix: enlarge to 3–4 cm minimum or shorten the content and regenerate. Quick test — photograph the code and zoom in: if modules blur together, phones cannot separate them either. Sizing numbers in size and print guide.
2 — Low contrast or busy background
Yellow on white, white on glass, code over a photo — all fail, especially in sunlight. Fix: reprint black on white with a quiet white margin. If branding insists on color, dark navy or maroon on white, then test outdoors at noon, not just office light.
3 — Glare, curve or physical damage
Glossy laminate glare, curved cups, cracked boards, sun-faded ink, crumpled receipts. Fix: matte reprint on a flat surface. The Pune glass-door sticker failed here too — moving the same code to a matte frame beside the door fixed it with zero redesign.
4 — Blurry file: JPG mush or upscaled small PNG
Forwarded-ten-times JPGs and 512px files stretched to posters both smudge module edges. Fix: regenerate at 2048px PNG and keep PNG masters archived. Upload the suspect image to the QR scanner — if even clean decoding struggles, the file is the problem.
5 — Wrong content format (silent failures)
WiFi strings with unescaped semicolons, malformed vCards, URLs missing https://. The camera scans fine but the action fails — the most confusing case. Fix: rebuild with the right tool — WiFi generator for networks (auto-escaping), vCard guide for contacts, full URLs for links.
Phone-specific checks (iPhone vs Android)
- iPhone: native camera reads QR since iOS 11 — no app needed. If nothing happens, check the code is not tiny and brightness is up; Control Center's Code Scanner works as backup.
- Android: most cameras scan natively; some need “Google Lens” mode or a long-press. Samsung's camera sometimes needs QR detection toggled on in settings.
- Old phones (pre-2018): fixed-focus cameras cannot resolve dense codes at all. Test with a sparse short-URL code at 4 cm before blaming the print.
- Low light: dim restaurants defeat cameras before codes. Add light on the sign, not a bigger code.
Prevention checklist: never diagnose again
Every fix above is cheaper as prevention. Tape this list next to whoever prints your codes — it is the entire guide compressed to six lines. Short URLs only; black on white with quiet margin; size per the distance rule; matte flat surfaces; PNG masters archived; one-copy test with two phones at real distance and light. I have not had a single bulk-print failure since adopting this ritual in 2024 — before that, two in one year. The ₹30 test print remains the highest-ROI thirty rupees in small-business marketing.
Reprint protocol: never waste a bulk order again
- Decode the suspect code with the QR scanner — confirm the content is even correct.
- Fix content first (shorten URL, correct format), regenerate PNG at the right size.
- Print ONE copy at 100%, matte, with quiet margin, “actual size” (no fit-to-page shrink).
- Test two phones, real distance, daylight + indoor. Pass? Order bulk. Fail? Walk the 5 causes again.