ID Badges: The Chest-Height Scan
ID badge QR codes — for access control, event check-in, or staff identification — are scanned at 20 to 30 cm, usually while the badge hangs from a lanyard or clip at chest height. The scan geometry is awkward by nature: the holder tilts the badge toward the reader while the reader points back, so the code is routinely scanned at an angle. Everything about badge codes should be optimized for tilted, hurried, repeated scanning.
The 10:1 Rule of Thumb
At 25 cm the rule suggests 25 mm; 20 mm is the practical standard on a CR80 card (85.6 × 54 mm — the credit-card size), which leaves room for the photo, name, and company branding that badges also carry. Keep the payload minimal — an ID number or short token, never a full profile. A short payload keeps the QR version low and the modules large, which is exactly what tilted scanning needs.
Recommended Size
Print at 20 × 20 mm (about 0.8 inches) on the badge front or back. Smaller than 15 mm invites failures, especially given the tilted scan angles badges endure and the varying quality of checkpoint lighting. If the badge design cannot fit 20 mm plus quiet zone, put the code on the back — scanners don't care which side it's on, and the front stays clean for human-readable identification.
Substrate and Printing
Badges print on PVC cards by dye-sublimation (direct-to-card) or retransfer printing. Retransfer — where the image is printed onto a film and then fused to the card — produces sharper module edges and is worth specifying for small codes; direct-to-card printing can leave slightly soft edges that cost reliability at 20 mm. Avoid placing the code over holographic security overlays or metallic inks, both of which destroy the contrast cameras need.
Placement and Practical Tips
- Keep the lanyard slot, clip hole, and any punched holes well clear of the quiet zone — plan the hole position before placing the code.
- Encode an opaque identifier and resolve permissions server-side; never encode access rights, personal data, or anything sensitive directly in a code that anyone with a phone can read.
- Test with the actual scanners at the actual checkpoints, in the venue's real lighting — phone cameras and dedicated imagers behave differently.
- Matte or satin card finishes scan more reliably than high-gloss under checkpoint lighting; specify accordingly.
- If badges are reprinted often (events, contractors), use a short stable URL pattern so old codes keep resolving.
Common Mistakes
- Encoding a vCard with photo and biography — the dense symbol won't survive badge-sized printing or tilted scanning.
- Holographic overlays or metallic inks crossing the code area, added by the security team without consulting the code layout.
- Glossy cards under harsh checkpoint downlights creating glare exactly where the code sits.
- Putting the only machine-readable credential on the front where lanyard clips and thumb wear degrade it fastest.