Poster QR code sizes
| Format | Usually scanned from | Minimum code width |
|---|---|---|
| A4 (noticeboard, window) | about 1 m (3 ft) | 10 cm (3.9 in) |
| A3 (shop, cafe, lift) | about 1.5 m (5 ft) | 15 cm (5.9 in) |
| A2 and A1 (hallway, campus) | about 2 m (6.5 ft) | 20 cm (7.9 in) |
| Bus shelter, six-sheet | about 3 m (10 ft) | 30 cm (11.8 in) |
Where poster codes get scanned
Posters earn scans where people stop: bus shelters, station platforms, lifts, cafe queues, campus noticeboards, waiting rooms. On a wall people walk past, the same code gets ignored. Put the code at about eye level, around 1.5 m (5 ft) from the ground, and print it larger than you think you need.
Test at the spot, on a phone, before the full run. A basement or an underground platform may have no signal, so the page won't open. Laminated and glossy posters can throw glare under shop lighting, and that is hard to see until you try to scan one.
Compare locations by scans per day on display, since posters rarely go up and come down together. Before you write off a venue with no scans, go and look. The poster may have been covered, moved or taken down.