GS1-128 Barcode Generator

FNC1: what makes it GS1 data

Every GS1-128 symbol starts with a special non-printing character called FNC1 — it's what tells a scanner "interpret what follows as GS1 Application Identifiers," rather than as arbitrary text the way a plain Code 128 barcode would be read. FNC1 also does double duty inside the barcode: GS1's variable-length fields (like a batch number, which can be anywhere from 1 to 20 characters) use a second FNC1 as a separator, marking exactly where that field ends so the next AI isn't misread as part of it. You never type FNC1 yourself — this tool's Studio inserts it automatically as part of rendering.

Common Application Identifiers

The five AIs this page's builder supports cover the large majority of real-world GS1-128 labels:

• (01) GTIN-14 — the product's global trade item number, 14 digits including its own check digit.
• (10) Batch/Lot — up to 20 alphanumeric characters identifying a production batch.
• (17) Expiry date — in YYMMDD format.
• (21) Serial number — up to 20 alphanumeric characters identifying one specific unit.
• (310x) Net weight, kg — a 6-digit value where x (0-5) sets how many of those digits are decimal places; 3102 with value 012345 means 123.45 kg.

GS1's full specification defines dozens more AIs for logistics, dates, and measurements beyond these five.

SSCC and logistics labels

GS1-128's home turf is the shipping label: pallets and cartons moving through a supply chain are almost always labeled with a Serial Shipping Container Code, AI (00), an 18-digit number uniquely identifying that one logistics unit end to end. A real-world pallet label routinely combines an SSCC with a GTIN (01), a batch/lot (10), and a quantity or weight field, all on the same GS1-128 symbol — exactly the kind of multi-field composition the AI builder above is built to make painless. That's the core reason GS1-128 exists as a distinct format: retail point-of-sale scanning wants one simple number, but a warehouse receiving dock needs several structured fields off a single label in one scan.

GS1-128 vs. plain Code 128

Physically, GS1-128 and Code 128 are the same symbology — identical bar patterns, identical checksum. The difference is entirely in convention: GS1-128 always opens with FNC1 and structures its data as Application Identifiers, while plain Code 128 encodes whatever text you give it with no implied meaning. Any scanner that reads Code 128 can decode the bars of a GS1-128 symbol too, but only GS1-aware software correctly parses the AI structure behind those bars. If your data isn't a GS1 field — an internal SKU, a tracking number your own system defines — plain Code 128 (see /code-128) is the simpler, more appropriate choice.