modbender Before Generating
- Choose correct type — URL is not the only option. See
types.mdfor vCard, WiFi, email, SMS, geo, etc. - Shorten dynamic URLs — Long URLs = dense codes = harder to scan. Use short links for tracking too.
- Set error correction — L (7%) for clean environments, M (15%) default, Q (25%) with logos, H (30%) for harsh conditions
Sizing Rules
Minimum sizes by scan distance:
- Phone at arm's length (~30cm): 2x2 cm minimum
- Table tent (~50cm): 3x3 cm
- Poster (~1m): 5x5 cm
- Billboard (~5m): 25x25 cm
Formula: QR size = scan distance ÷ 10
Color & Contrast
- Minimum 70% contrast between foreground and background
- Dark on light ONLY — scanners expect dark modules
- Never invert (white on black fails on many readers)
- Avoid gradients on modules — solid colors only
- Background can have subtle texture if contrast maintained
Testing Checklist
Before printing/deploying:
- Scan with 3+ different phones (iOS, Android old/new)
- Test in target lighting conditions
- Verify destination loads correctly
- Check at actual print size, not screen preview
- Test after any logo/customization applied
Common Failures
| Symptom | Cause | Fix |
|---|---|---|
| Won't scan | Too small / low contrast | Increase size, check colors |
| Scans but wrong content | URL changed after print | Use dynamic QR / redirect |
| Works on some phones | Over-customized, low error correction | Reduce customization, increase EC |
| Slow to recognize | Too dense | Shorten URL, reduce data |
Use Case Guides
| Context | See |
|---|---|
| Data types (WiFi, vCard, etc.) | types.md |
| Business deployment patterns | deployment.md |