What you are seeing
The printed code shows horizontal or vertical bands running through it: stripes of lighter or darker ink that break up the modules. Banding comes from the printer, not the artwork, and the screen version looks clean, which is why it surprises people. A band that crosses a finder pattern or a data area can corrupt enough modules to make the code fail or slow down badly. The fix is a printer fix, not an artwork fix, so start at the printer.
Likely causes
1.
Clogged or misaligned print head — A nozzle that is blocked or a head that is misaligned lays down uneven ink, which shows as stripes. Test: print the printer's nozzle check or alignment page.
2.
Draft or high-speed print mode — A fast or economy mode can leave visible bands where the head passes overlap unevenly. Test: reprint the same file at normal or high quality.
3.
Low ink or toner — A cartridge running low can fade in bands as the supply varies. Test: check the ink or toner levels and print a test page.
4.
Paper feed problem — A roller that slips or a sheet that feeds unevenly can leave a band where the feed stuttered. Test: check whether the bands appear in the same place on every copy.
5.
Wrong media setting — A printer set for the wrong stock can lay down the wrong amount of ink for that surface, which shows as banding. Test: confirm the media setting matches the stock.
Step-by-step fix
1. Print the printer's nozzle check and alignment page and fix any fault it shows.
2. Clean the print head using the printer's cleaning routine, then reprint the test page.
3. Switch the print mode to normal or high quality, not draft or high-speed.
4. Check the ink or toner level and replace a low cartridge.
5. Confirm the media setting matches the stock you are using.
6. Reprint one proof and confirm the bands are gone before approving the run.
Putting this into practice
In practice, banding is a printer maintenance signal. A printer that bands on a QR code is banding on everything else too, so the fix helps every job, not just this one. Build a short printer check into the start of any important run: nozzle check, test page, then the proof. Keep a short note of what you tested, what failed, and what you changed, so the next person starts from evidence rather than guesswork. A fix that is written down survives staff changes and reprints; a fix that lives only in memory gets repeated.
Common mistakes to avoid
- Reprinting the full run on a banding printer in the hope that the next copies will come out clean.
- 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 prints with banding lines will be used.
- Changing the artwork and the placement at the same time, so you cannot tell which change fixed a code that prints with banding lines.- Skipping the proof test because the change looked small, when small changes cause most repeat failures.
Quick checklist
- The nozzle check and test page are clean
- The proof shows no banding lines
- The proof scans on two phones
- 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)
