QR Code Generator

What a QR code actually stores

A QR code is a 2D barcode that encodes a short string of data as a grid of black and white modules. It does not store a website, a file, or a contact card in any rich sense — it stores text, and a scanning app interprets that text by convention. "https://example.com" is read as a URL to open; "WIFI:S:MyNet;T:WPA;P:secret;;" is read as Wi-Fi credentials; a block of vCard text is read as a contact. The QR standard is an international one, ISO/IEC 18004; the technology was invented by Denso Wave in 1994 for tracking car parts.

Capacity is finite and depends on the data type and the error-correction level you choose. A QR code can hold thousands of numeric digits but far fewer bytes of arbitrary text, and the more you cram in, the denser the grid becomes — which makes it physically harder to scan. Short payloads are not just neater; they're more reliable.

Error-correction levels: redundancy vs density

Higher correction means the code still scans with part of it damaged or covered — at the price of a busier grid. If you overlay a logo, use H so the obscured center is recoverable.

Making a code that actually scans

• Keep the quiet zone. The QR spec requires a clear margin of at least four modules of empty space around the code. Crop it flush to the edge or place text right against it and many scanners fail.
• Respect minimum size. A rough rule for print is a scanning distance about 10x the code's width — a 2 cm code is reliable at roughly 20 cm. For a poster read across a room, make it big.
• Keep high contrast and correct polarity: dark modules on a light background. Inverted (light on dark) codes are non-standard and many readers reject them.
• Prefer short payloads. Shorten a long URL before encoding it — a shorter string yields a lower-density, more forgiving grid.
• Test before you print or publish. Scan the generated code with two or three different phones; a code you can't un-print is an expensive mistake.

Payload types and a safety note

Beyond URLs, the common encodings are Wi-Fi network credentials (network name, security type, password), vCard or MECARD contact details, plain text, email and SMS templates, and geo-coordinates. Each is just a specially formatted string the scanner recognizes — there's no magic, which is also why the data is only as private as the medium you print it on. A Wi-Fi QR code on a public wall hands your password to anyone who walks past.

Because a QR code is opaque to humans, it's a phishing vector: you cannot see that a code leads to a malicious site until you scan it ("quishing"). Treat codes from untrusted sources with the same caution as shortened links. If you've scanned a code and want to see where it really points before acting on it, decode and inspect it with QR Inspector.