How QR Codes Work

ficklestudio26 · Facts checked October 25, 2026

A QR code is a grid of black and white squares that stores text, usually a web address. Its design includes a repair system, which is why a code can still scan when partly damaged.

Make a QR code
Create a code for a link, text or Wi-Fi, on your device.
Open the tool →

Where it came from

The QR code was invented in 1994 by Masahiro Hara at the Japanese company Denso Wave, to label automobile parts. Its standard is ISO/IEC 18004. The company holds patents but has used them in a limited way: use is free as long as the code follows the published standard.

Versions and size

QR codes come in versions 1 to 40. Version 1 is 21 × 21 modules (the small squares), and each step adds 4 modules per side, so the size is 4 × version + 17. Version 40 is 177 × 177. Bigger versions hold more data. At level L, version 40 holds up to 7,089 digits, 4,296 letters and digits, or 2,953 bytes.

The four error correction levels

The code stores extra repair data. The level sets how much of the code can be restored if it is dirty or covered:

L: about 7%
M: about 15%
Q: about 25%
H: about 30%

The trade-off is simple: a higher level means more repair data, so the same text needs a denser, larger-version code.

Tips for a code that scans

Shorter text makes a simpler code with bigger squares, which is easier to scan from a distance.
Keep strong contrast. Dark squares on a light background work best.
Leave a blank margin around the code.
Test with more than one phone before printing a large run.
Use level M or Q if you plan to place a logo in the middle; the logo covers part of the data.