QR code: what the squares hold and why length matters

A QR code is a two-dimensional barcode that stores text — most often a URL — as a grid of black and white squares called modules, with three large finder patterns in the corners so a camera can locate and orient it.

Length decides everything else

More characters means a higher version, which means more modules in the same physical square, which means each module is smaller and harder for a camera to resolve. A short URL is not a cosmetic improvement here: gc.mw/abcd produces a visibly coarser grid than a 90-character tracking URL, and a coarser grid scans from further away, in worse light, at a smaller print size.

Error correction works against you in the same direction. Level H recovers the code with roughly 30% of it damaged or covered — which is what makes a centre logo possible — but it spends capacity to do it. Our generator uses level M by default and switches to H automatically whenever a logo is requested, capping the logo at 30% of the width. Short input plus high correction is the combination that survives a scuffed table sticker.

How gc.mw generates one

Every link has a QR at gc.mw/{code}.qr for a PNG and gc.mw/{code}.svg for vector. Size runs from 96 to 2,048 pixels, foreground and background take hex colours, and the images are cached for a day, so a code on 50,000 flyers costs nothing to serve. Workspaces on plans with branded QR can add rounded or dot module styles and a centre logo; on plans without it those parameters are ignored rather than rejected, so an embedded image keeps working after a downgrade instead of breaking.

The encoded URL carries a qr marker, which is why scans are attributed separately. A QR for a blocked or archived link returns 404 rather than an image.

Printing rules that actually matter

Use the SVG for anything printed. Keep a quiet zone of four modules of clear space on every side. Two centimetres across is the floor for a code held at arm's length; a poster read from three metres needs something closer to 30. Keep the contrast high and dark-on-light — inverted codes fail on a surprising number of camera apps.

Example

A table sticker with gc.mw/menu at 3 cm, SVG, black on white, error correction high. The menu changed hosts twice; the stickers were printed once.

Build a code for a link, text, Wi-Fi or a contact card with the QR code generator.