How it works
A structured append header comes first in each symbol. It starts with the mode indicator 0011, then 4 bits for the symbol’s position in the sequence and 4 bits for the total number of symbols, then an 8-bit parity value.
The parity byte is the XOR of all bytes of the original message, and every symbol in the set carries the same value. A reader uses it to check that the codes it has collected belong together.
- Up to 16 symbols per message
- Header: mode indicator, 4-bit position, 4-bit total, 8-bit parity
- Symbols can be scanned in any order
- Each symbol can use its own version and error correction level
When it is used
Structured append was designed for data too large for one symbol, or for fitting data into a long narrow space as a row of smaller codes. It appears mostly in industrial and document applications with dedicated scanners.
Consumer phone camera apps rarely support it. They typically read each symbol on its own and show the fragment, so for public-facing uses a single code with a short link to the full content is more reliable.