Identifier types — not a law

Product identifiers

ImplementedListrar implements this standard on every public record.

Listrar summary

A product carries more than one identifier, and they are not interchangeable. A GTIN names a trade item globally and is what a barcode encodes; a SKU is a retailer's own internal stock code and means nothing outside that retailer's systems; an MPN is a manufacturer's catalogue number, useful for sourcing but not resolvable; a serial number names one physical unit, not the product line. A Digital Product Passport resolves through the one identifier meant to be public and shared: the GTIN, carried as a GS1 Digital Link address.

Who does it apply to?

Anyone deciding which number to put in a Digital Product Passport or a public product record
Catalogue and PIM teams reconciling GTIN, SKU and MPN across systems
Item-level passports (batteries, for instance) that add a serial number beneath the GTIN

Main obligations

None in law directly: ESPR requires a resolvable identifier without naming one scheme, but the GTIN is the de-facto answer the rest of retail and logistics already uses
Keep exactly one identifier public and resolvable per product; internal codes (SKU, MPN) stay internal
Where item-level identity matters, pair the GTIN with a serial number rather than replacing it

Key dates

1970s: Retail barcoding introduces the Universal Product Code, the GTIN's ancestor
2005: GS1 consolidates GTIN, GLN, SSCC and the other identifier keys into one system
2024: ESPR requires a resolvable product identifier without mandating a single scheme

Products in scope

GTIN — the public, resolvable identifier a barcode and a passport share
SKU — a retailer's internal stock code, not unique outside that retailer
MPN — a manufacturer's catalogue number, useful for sourcing, not for resolving
Serial number — one physical unit, layered under the GTIN where item-level identity matters

Obligations by actor

Brand: Assigns the GTIN and decides which internal codes (SKU, MPN) map to it
Retailer: Maps its own SKU to the brand's GTIN rather than replacing it
Registry: Resolves the public record from the GTIN, never from an internal code
Verifier / lab: Cites the GTIN, not an internal code, when reporting on a specific product

Documents and evidence to keep

The mapping table from internal codes (SKU, MPN) to each product's GTIN
Which identifier is published publicly versus kept internal, and why
For item-level passports, the serial-to-GTIN pairing

Sanctions and risks

No legal sanction for the mapping itself — the risk is operational
Publishing a SKU instead of a GTIN produces a passport nothing outside the company can resolve
A GTIN reused across two different internal codes breaks matching everywhere the GTIN is trusted as unique

Key references

GS1 identifier keys — GTIN and its siblings inside GS1's one identifier system