Printing a QR code: size, contrast and scanning distance

The 10:1 rule

The minimum size of a printed QR depends on scanning distance: allow roughly 1 cm of width per 10 cm of distance. A QR scanned at 30 cm (business card) must be at least 3 cm; a poster read at 3 meters requires 30 cm.

Non-negotiable contrast

The reader distinguishes modules from background by luminance contrast, not by color. Dark modules on a light background: always. Avoid light modules on a dark background (some readers handle it, many fail), and beware of gradients that reduce local contrast.

Vector for print

An enlarged PNG becomes blurry; an SVG stays sharp at any size. For professional printing, always export web3qr's SVG and import it into your layout (Illustrator, Inkscape, Figma). If a printer demands raster, generate a PNG at 300 DPI minimum.

Quiet zone

Keep a white margin of at least 4 modules around the code (the "quiet zone"). Text or a logo encroaching on this zone can prevent detection. web3qr's batch templates (business cards 2×5, stickers 3×4, menus 1×1) include these margins automatically.

Test before the print run

Print a test page, scan with two different phones at the real usage distance, in normal AND low light. A failure at this stage costs one sheet; after the print run, it costs the campaign.