# GTIN — Global Trade Item Number

> The GTIN registry row: four lengths, one 14-digit identity; GS1 mod-10; symbology bindings; license-clean enrichment rails.

- page: https://barcoding.dev/schemes/gtin/
- machine row: https://barcoding.dev/schemes/gtin.json
- scheme (dotted registry name): gs1.gtin

## Reference
- grammar: 8, 12, 13 or 14 digits (GTIN-8/12/13/14); the final digit is the check digit. Four lengths, one identity: canonicalization zero-pads to the 14-digit form.
- check: GS1 GenSpecs mod-10, right-anchored — alternating 3/1 weights from the rightmost data digit; the check digit makes the weighted sum a multiple of ten.
- canonical: The 14-digit zero-padded form. GTIN + serial derives urn:epc:id:sgtin; GTIN + lot derives urn:epc:class:lgtin.
- barcode types: UPC-A · EAN-8 · EAN-13 · ITF-14 · GS1-128 (AI 01) · GS1 DataMatrix / QR via element string or Digital Link URI
- enrichment: food: USDA FoodData Central (CC0, public-domain) · Open Facts family (ODbL, segregated share-alike layer)
- join: epcList (serialized) or quantityList (lot/class grain) of an EPCIS 2.0 ObjectEvent — the AI map decides the grain.

## Registry rows (engine artifacts, digest-stated)
### gs1.gtin
- grammar: `^\d{8}$|^\d{12}$|^\d{13}$|^\d{14}$`
- check: mod10 → "mod10 pass" (GS1 GenSpecs 26.0 §7.9)
- canonical: GTIN-14: zero-pad to 14 digits
- segments: indicator / number system · company prefix · item reference · check
- generate: ean13, upca, itf14, gs1-128, gs1datamatrix, qrcode
- hand-off: read here · resolved by id.org.ai
- digest: sha256:e426d368687d9a244454dc4198fcb210ce9aaa134603fa99fb5ae4fb9ebc9cd6

## Resolution stance
barcoding.dev detects, parses, verifies, enriches and generates — the codec and the data layer. Resolution — an identifier answered with identity and its linkset of live doors — is ONE capability family-wide, served by the family's identity layer, id.org.ai; vertical estates project the same one capability (vehicles: auto.dev). This registry row is the data that resolution consumes.

## Posts
- https://barcoding.dev/blog/gtin-four-lengths-one-identity/
- https://barcoding.dev/blog/the-upc-is-a-checkout-token/
- https://barcoding.dev/blog/isbn-is-a-gtin/
- https://barcoding.dev/blog/ndc-no-check-digit/
- https://barcoding.dev/blog/bridge-sku-to-gtin/