Structured append

How it works on paper

Each symbol in the set opens with the structured append mode indicator 0011, followed by a 4-bit sequence index, a 4-bit total count (hence the 16-symbol maximum) and an 8-bit parity byte — the XOR of all bytes of the complete message, identical in every symbol, so a reader can tell that the parts it collected belong to the same message. In theory that multiplies capacity sixteen-fold: sixteen version-40 symbols could carry about 47 KB.

Why it does not work in practice

Reassembly is the reader's job, and mainstream readers never took it on. iOS and Android camera apps treat each symbol as an independent code and act on the first one they see; ZXing's support is partial and most wrapper apps ignore it. A multi-part code printed for the public will behave as one working code and several confusing ones.

If a payload does not fit in one symbol, the honest fixes are: shorten it, host the content and encode a short URL instead (why longer URLs make denser codes), or split the task rather than the data. Structured append survives only in controlled industrial settings where the operator chooses a scanner that implements it.

FAQ

Can one QR code continue into another?

The standard allows it — structured append chains up to 16 symbols with sequence numbers and a parity check. But phone cameras do not reassemble them, so for any public audience the answer is effectively no.

How do I encode more data than one QR code holds?

Do not. Host the data at a URL and encode that instead; a shorter payload also produces a sparser, more scannable code. Multi-symbol sets only work with dedicated scanners chosen for the job.