QR code test: check a QR code before you print it
Upload or paste a QR code image to test it. Nothing is uploaded: it is checked in your browser.
Drop a QR code image here, or choose one.
or paste an image (Ctrl/Cmd+V)
What the test checks
- Decoders: two decoders (jsQR and zxing-cpp) read it. Only one: warning.
- Contrast: 4.5:1 or more passes, 3:1 to 4.5:1 warns, under 3:1 fails.
- Quiet zone: an empty margin of 4 modules passes, 2 to 4 warns, under 2 fails.
- Colours: dark modules on a light background pass. Inverted codes warn.
- Size: the module count gives the minimum print width (0.4 mm a module, at least 2 cm) and the scan distance (10 × the width).
Why test a QR code before printing
A reprint costs more than a test. Most codes that fail in print look fine on screen: the colours are too close, the margin was cropped by the layout, or the code was printed too small for the distance people stand at.
This QR code checker reads your image with two decoders and measures what printers and phone cameras care about: the contrast between the dark and light modules, the empty margin around the code, whether the colours are inverted, and the module count, which sets the minimum print width.
Each check is Pass, Warn or Fail, with a link to the fix. A Pass means the file is sound; still print one copy and scan it with two phones in the real light.
Questions
- How do I test a QR code before printing?
- Upload the exact file you will send to the printer. The test reads it with two decoders and checks contrast, the quiet zone, the colours and the size. Then print one copy and scan it with two phones from the real distance.
- What contrast does a QR code need?
- A contrast ratio of at least 4.5:1 between the dark and the light modules passes. Between 3:1 and 4.5:1 most phones still read it, so the test warns. Below 3:1 it fails.
- What is the quiet zone?
- The empty margin around the code. It should be at least 4 modules wide on every side. Under 2 modules, many phones cannot find the code at all.
- Is my image uploaded anywhere?
- No. The image is decoded by JavaScript in your browser. It is never sent to Pretty QR or to anyone else, and nothing is stored after you close the page.
- Do I need an account?
- No. The scanner and the print test are free and work without signing up.