Payload

A payload is the actual body of the data you want to convey in a communication packet or data structure, excluding the control information (headers, metadata, error correction). The word comes from the payload (cargo) of a rocket, and it means "the main body that has to be carried".

The payload of a QR code is the portion holding the data the user stored (a URL, text, contact information, and so on), excluding the error correction codewords and the format information. The proportion of the total number of codewords in a QR code that can be used as payload changes with the error correction level. Of the 3,706 codewords in total at version 40, 2,956 (about 80%) can be used for data at level L, while at level H the figure stays at 1,276 (about 34%). The figures of about 7% / about 30% attached to the level names are the proportions of damage that can be restored, not the proportions of the payload.

The maximum size of the payload is determined by the QR code version and the encoding mode. At the largest version, 40 (177 by 177 modules), with level L, the upper limit of the payload is 7,089 characters for numbers, 4,296 characters for alphanumerics, and 2,953 bytes for byte data. In practice, most cases store a URL or a short text, and reaching this upper limit is rare.