What are the brackets in a GS1-128 code?

A human-readable convention only. The parentheses around an AI are printed under the barcode for people to read; they are not part of the encoded data.

Why does my scan produce garbled fields?

A missing GS separator after a variable-length field. Without it the parser keeps consuming digits into the next AI, and everything downstream is wrong.

Serial Shipping Container Code, AI (00) — an 18-digit identifier for a logistics unit such as a pallet, unique enough to track that specific unit through a supply chain.

GS1-128 Barcode Decoder

Parse GS1-128 application identifiers out of a barcode data string.

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The gs1-128-decoder decoder is on the roadmap. The heavier binary and cryptographic parsers ship after the core text and token decoders — all of which are already live and working.

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What is the GS1-128 Barcode Decoder?

A GS1-128 decoder splits a barcode data string into its Application Identifiers — two- to four-digit codes such as (01) for GTIN, (10) for batch and (17) for expiry — and the value that follows each one.

GS1-128 carries structured data rather than a single number. Each field opens with an Application Identifier that defines what the field means and how long it is: (01) is a 14-digit GTIN, (17) a 6-digit expiry date as YYMMDD, (10) a variable-length batch or lot, (21) a variable-length serial number, (00) an 18-digit SSCC identifying a logistics unit.

The fixed-versus-variable distinction is the whole parsing problem. Fixed-length AIs can simply be read off in sequence, but a variable-length field runs until a GS separator character (ASCII 29) or the end of the string. Miss a separator and every field after it is misread — the usual cause of a pallet label that scans but produces nonsense.

This is the encoding behind pharmaceutical serialisation, food traceability and logistics labels, where a single scan must yield product, batch, expiry and serial at once.