Module

A module is the square cell that is the smallest unit making up a QR code. It takes one of two values, white or black, and represents a bit of data (0 or 1). It is sometimes called a "dot" of the QR code, but in the technical specification its formal name is module.

The version (size) of a QR code is determined by the number of modules on one side. The smallest, version 1, consists of 21×21 = 441 modules, and the largest, version 40, consists of 177×177 = 31,329 modules. The higher the version, the more data can be stored, but either the printed size becomes larger or each module becomes smaller.

The module size when printed is directly linked to reading accuracy. For stable reading with a typical smartphone camera, 0.5mm or more per module is the guideline. For a version 10 QR code (57×57 modules), a printed size of at least about 28.5mm square is required. This lower limit changes depending on printing precision and reading distance, and when high-definition printing is read at close range, it can sometimes be made smaller.