A QR code version is a number from 1 to 40 that defines the code's size and data capacity. Version 1 is the smallest, with a 21x21 module grid, and each subsequent version adds 4 modules per side. Version 40, the largest, has a 177x177 module grid. Higher versions can store more data but produce larger, more complex codes.
The version is automatically selected based on the amount of data to encode and the chosen error correction level. A short URL of 20 characters with medium error correction might require only Version 2 (25x25 modules), while a long URL of 200 characters might need Version 10 or higher. QR code specification books on Amazon detail the version specifications.
For URL shortening, the relationship between URL length and QR code version is a key motivation. A shorter URL results in a lower version number, which means fewer modules, a simpler visual pattern, and better scanning reliability at small print sizes or from greater distances.
When generating QR codes for print materials, it is important to consider the minimum module size for reliable scanning. Each module should be at least 0.33mm for close-range scanning. Lower version QR codes can be printed smaller while maintaining this minimum module size. Print design books on Amazon cover sizing guidelines.