Glossary
Version information
Version information is an 18-bit block present only in QR codes of version 7 and above, recording the code's size. Smaller codes do not need it because the decoder can count modules directly.
Structure
6 data bits for the version number plus 12 Golay error-correction bits, stored twice — once near the top-right finder pattern and once near the bottom-left.
Why only version 7 and up
For a small code, counting the modules between finder patterns is unambiguous. As codes get larger, accumulated sampling error makes a miscount plausible, so the version is stated explicitly.
The threshold at version 7 (45 × 45 modules) is a spec decision, not a physical boundary.
Related
- Version — A QR code's version is its size: version 1 is 21 × 21 modules and each step adds 4 modules per side, up to version 40 at 177 × 177. The encoder picks the…
- Format information — Format information is the 15-bit block next to the finder patterns that records the error-correction level and mask pattern. It is stored twice and…
- Module — A module is one square cell of a QR code — the smallest unit of the pattern. Codes are measured in modules, not pixels or millimetres, because the module…