What you are seeing
This fix takes a code that passes on screen and makes it pass on paper. You will print a single proof on the real stock, find which print property broke it, and correct the artwork or the print settings. Do not approve a full run from a screen test. Approve it from a printed proof scanned in the real lighting.
Likely causes
1.
Wrong file type or resolution for print — Quick test: check the export type and pixel size against the printed size.
2.
Ink spread on absorbent stock — Quick test: compare the printed modules with the digital file under magnification.
3.
Colour shift on the real printer — Quick test: print a plain black-on-white proof and see whether it scans.
4.
Glossy stock reflections — Quick test: tilt the proof and shade it to see whether scanning improves.
5.
Size shrunk to fit the layout — Quick test: measure the printed code and compare it with the designed size.
Step-by-step fix
Step 1: Export a fresh print file as a vector, or as a raster sized for the exact printed dimensions.
Step 2: Print one proof on the real stock and the real printer. Do not judge the run from a different printer or paper.
Step 3: Scan the proof in the real lighting on two phones, and compare the printed modules with the digital file.
Step 4: If the modules look thickened, increase the code size, raise the contrast, or switch to a less absorbent stock.
Step 5: If reflections are the problem, switch to matte stock or move the code away from direct light.
Step 6: Reprint a single corrected proof and scan it at the real distance on two phones.
Step 7: Approve the run only after the corrected proof passes, and check the first copies off the printer against it.
Putting this into practice
In practice, keep the approved printed proof with the job file and mark it as the reference. When a reprint fails, comparing the new copies with that proof tells you immediately whether the artwork, the stock, or the printer changed. Record the before-and-after behaviour with the job file, so the fix is provable rather than anecdotal. When the same failure appears again, that record tells you whether the old fix held or a new cause appeared.
Common mistakes to avoid
- Approving a full print run from a screen test and discovering the failure only after hundreds of copies are printed.
- Reprinting the full run before a single proof passes, which turns one failure into many.
- Testing on one phone in ideal conditions instead of two phones in the real conditions where a code that works on screen but not in print will be used.
- Changing the artwork and the placement at the same time, so you cannot tell which change fixed a code that works on screen but not in print.- Skipping the proof test because the change looked small, when small changes cause most repeat failures.
Quick checklist
- The print file is vector or high-resolution at the printed size
- One proof on the real stock scans on two phones
- The printed modules match the digital file without thickening or glare
- The corrected proof passes on two phones in the real conditions
- The fix is recorded in the job file so the next reprint starts from a proven setup
- Every printed copy is checked against the approved proof
- The proof is retested after any later change to the link, design, or placement
Related tools and guides
- [QR minimum size checker](/qr-minimum-size-checker)
- [QR contrast checker](/qr-contrast-checker)
- [QR print proof checklist](/qr-print-proof-checklist)
- [QR DPI calculator](/qr-dpi-calculator)
- [QR quiet zone calculator](/qr-quiet-zone-calculator)
- [printed QR tester](/printed-qr-tester)
- [QR size calculator](/qr-size-calculator)
