The short answer
Start with the final physical size and scan distance, not only the pixel size of the PNG. Keep the pattern crisp, leave clear space around it, and test a sample in the environment where people will scan it.
The generator’s pixel setting controls image output. It does not promise a physical print size because printers and layouts scale images differently.
Protect the quiet zone
The quiet zone is the blank space around the outside of the code. Keep at least four modules clear on every edge and avoid placing the code flush against a border, photo, or busy label.
Edge space
4 modules
Pattern
Crisp
Proof
Real sample
Use contrast before decoration
A dark foreground on a light background is the dependable starting point. Logos, captions, gradients, and low-contrast colour choices can reduce the margin for error and should be tested rather than assumed safe.
- Prefer dark pattern and light background.
- Avoid transparent or photographic backgrounds.
- Keep the code away from folds and curved surfaces.
- Check the final print under the lighting people will use.
Test at the intended size
Print one sample at the intended size and scan it from the expected distance with more than one current phone if the batch matters. Original scan-test data for this project is still pending, so no universal millimetre benchmark is claimed here.
Open print tips in the generator