QR code checker
Drop your file or a photo of the proof: the tool reads it the way a phone would, then measures what could make it fail once printed.
Updated September 24, 2026
Test your QR code before printing
Drop the exported file or a photo of the proof. We measure what a phone sees.
What the checker measures
| Check | Good | Watch | Fix |
|---|---|---|---|
| Decoding | Code read | No code read | |
| Module to background contrast | 4.5:1 or more | 3 to 4.5:1 | Under 3:1 |
| White margin | 4 modules or more | 2 to 4 modules | Under 2 |
| Module size in the file | 4 pixels or more | 2 to 4 pixels | Under 2 |
| Colors | Dark on light | Light on dark | |
| Density | Up to 41 by 41 modules | Up to 61 by 61 | Beyond |
These are the thresholds the QRTada designer enforces: contrast under 3:1 blocks the download, 3 to 4.5:1 shows a warning. The 4-module margin comes from ISO/IEC 18004. Contrast is computed like in web accessibility (the WCAG luminance ratio), between the average dark module and the average background.
Reading the results
Contrast is the most common reason branded codes fail. Light pink on blush, gray on beige: fine on screen, hit or miss on glossy paper under fluorescent light. Keep modules very dark on a very light background.
The white margin (quiet zone) tells the phone where the code starts. A photo cropped tight around the pattern can show a small margin even if your file is fine; in that case check the full layout instead. The glossary explains the quiet zone in detail.
Module size in pixels is about the file, not the print. Under 4 pixels per module, edges blur once enlarged. Export as SVG, a lossless vector format, or as a large PNG.
Density depends on how much data the code holds. A long URL or a full vCard produce a tight pattern that needs a large print. A dynamic code always holds a short link, so its pattern stays airy. The size calculator gives the minimum print size by distance and density.
What the checker cannot measure
- Error correction level (L, M, Q or H): our reader cannot extract it reliably from an image. Pick H when the code carries a logo.
- Paper behavior: gloss varnish, foil or textured stock create glare that only a real proof reveals.
- The destination: the tool reads the link, it does not check the page exists. Open it yourself.
A full pre-print test
- Run the final file through this checker.
- Print a proof at real size, on the real paper.
- Scan it with two different phones, one of them older, from the planned distance.
- Test under the actual lighting: fluorescent, evening light, a sunny window.
The QRTada designer does step one automatically: every code is re-read before download, and an unreadable code cannot be downloaded.
Frequently asked questions
Does it work with codes made elsewhere?
Yes, it reads any standard QR code, whatever tool created it.
Can I test a photo of my poster?
Yes. Shoot it straight on and close enough; the measured margin depends on how you crop.
My code scans but contrast says "watch". Is that bad?
It will read in good conditions but fail more often in low light or with older phones. Darken the modules to be safe.
Is my file uploaded to QRTada?
No, the analysis runs in your browser and nothing is stored.
Sources
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