A scannable QR code for your shop window: size, material, glare

A QR code in your window only works if people can actually scan it — from the pavement, in one try. Most failures come down to four fixable things: size, contrast, the white margin, and glare. Here's how to get it right.

Size: the 10-to-1 rule

The reliable rule is a distance-to-size ratio of about 10:1. If passers-by scan from 70 cm, make the code ~7 cm wide; from 1 metre, ~10 cm. The minimum that holds up in the real world is roughly 3–4 cm, but a window is scanned from further than a table — so err big. A too-small code is the most common rookie mistake.

Contrast & the quiet zone

Two things make or break a scan:

• High contrast — dark modules on a light background, ideally black on white. Never light-on-dark, never a busy photo behind it.
• The quiet zone — the empty white margin around the code, at least four modules wide. It's the single most common reason QR codes fail. Don't crop it, don't let text or a border touch the code.

Beating glare on glass

Glass and gloss are the enemy: overhead lights or sun reflect straight into the camera and wash out the contrast. Fixes: choose a matte finish (not glossy), avoid spots in direct sun, and on a transparent decal add an opaque white backing behind the code so it doesn't pick up whatever is behind the glass.

Material & mounting

Use a proper window sticker (vitrophanie). Inside the glass is protected from weather and tampering (mirror-print if it faces outward through the glass); outside is easier to scan but more exposed. Mount it at eye level — our guide on the best spots in your window covers placement in detail.

Add a short prompt — and test

People won't scan a bare code. Add one line beside it (“Scan for our hours & menu”). Then test before you commit: print two or three sizes, stick them up, and scan from the pavement with a couple of different phones, in bright and dim light.