QR code

The parts, at a glance

Every QR code is a square grid of modules — from 21 × 21 at version 1 to 177 × 177 at version 40. Three corner finder patterns let a scanner locate and orient the symbol from any angle, timing patterns calibrate the grid, alignment patterns correct perspective, and a quiet zone of clear space frames it all. The data itself is protected by Reed–Solomon redundancy at one of four error correction levels, so up to 30% of the pattern can be damaged and still decode.

"QR" is short for Quick Response: Masahiro Hara's team at Denso Wave built it in 1994 to track car parts faster than linear barcodes allowed. Denso Wave holds patents but has never exercised them against standard-conforming use, which — together with the open ISO/IEC 18004 specification — is why anyone can generate and read QR codes without paying or asking.

What a QR code contains

Nothing but data. A payload — a URL, WiFi credentials, a vCard, a payment string — is encoded once, at generation time. A static code never changes and never expires; a dynamic code stores a redirect URL owned by a service instead. Smaller and rectangular relatives exist for tight spaces: Micro QR and rMQR.

FAQ

What does QR stand for?

Quick Response. The name refers to decode speed — the design goal at Denso Wave in 1994 was a code that scanners could locate and read faster than the stacked barcodes of the time.

How much data fits in a QR code?

Up to 7,089 digits, 4,296 alphanumeric characters or 2,953 bytes at the largest size with the lowest error correction. Practical codes stay far smaller — a URL of under 100 characters scans best.

Are QR codes free to use?

Yes. The specification is an open ISO standard, Denso Wave permits standard use of its patents, and the "QR Code" trademark only restricts using the name for other products — not making or scanning codes.