Glossary
ISO/IEC 18004
ISO/IEC 18004 is the international standard defining QR codes: symbol structure, encoding, error correction, masking and decoding. It is the authoritative reference, and it is why codes from any generator read on any scanner.
What it covers
Symbol sizes (versions 1–40 and Micro QR M1–M4), the four encoding modes, Reed–Solomon parameters per version and level, the eight mask patterns and their penalty scoring, format and version information encoding, and the required decoding procedure.
Revisions
The 2000 edition, the 2006 edition (adding Micro QR), and the 2015 edition, which is the current base. Rectangular rMQR is defined separately in ISO/IEC 23941:2022.
Why interoperability actually holds
Because the standard specifies the decoding procedure, not just the encoding, a conforming decoder must handle any conforming symbol. That is why a code generated by a Japanese industrial printer in 2003 still reads on a phone made this year.
The standard is not free to download; national bodies sell it. Implementers generally work from it plus open-source references such as ZXing.
Related
- Denso Wave — Denso Wave is the Japanese company that invented the QR code in 1994, and it holds the patents. It chose not to enforce them for use of the standardised…
- 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…
- Mask pattern — A mask pattern is one of eight XOR patterns applied to a QR code's data area to avoid large blocks of one colour and false finder-like shapes. The encoder…