QR Code Generator

Error correction is the setting that matters

QR codes use Reed-Solomon error correction at four levels: L recovers about 7 percent of the data, M about 15, Q about 25 and H about 30. Higher correction means more redundancy, which means a denser code for the same content. Level M is the sensible default for a screen or a clean print. Use Q or H only when the code will be printed small, on a curved or textured surface, or where a logo will be placed over the centre, since that logo is damage as far as the decoder is concerned.

Size and quiet zone

The specification requires a quiet zone of four modules of blank space on every side. Codes that fail to scan often fail because a designer cropped that margin or placed the code against a busy background. As a rule of thumb the code should be at least a tenth of the scanning distance across: a poster read from two metres needs roughly a 20 centimetre code.

Shorter data scans faster

Every additional character raises the version number and packs more modules into the same physical area, making each module smaller and harder for a camera to resolve. A short URL scans reliably at a size where a long one with tracking parameters will not. If you need campaign tracking, use a redirect service rather than appending a long query string.

Static versus dynamic

A QR code encodes fixed data. Once printed, the destination cannot be changed. If the URL might ever move, encode a URL you control that redirects, so you can repoint it later. This also gives you scan analytics. The trade is that the redirect must keep working indefinitely, which is a real commitment: a dead redirector silently breaks every code you ever printed.

Contrast and inversion

Dark modules on a light background is what decoders expect. Inverted codes work in some readers and fail in others, and low-contrast colour pairs fail widely. Keep a strong luminance difference and test with more than one phone before printing at scale.

Generated locally

Encoding happens in your browser, so Wi-Fi passwords and contact details you encode are never transmitted.

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