GTIN, MPN, EAN: which product identifiers does your feed actually need?

Three letters — GTIN, MPN, EAN — cause a disproportionate amount of confusion in product feed management. Here are practical answers for UK merchants.

What each identifier actually is

GTIN is the umbrella term for all barcode-based product identifiers. EAN, UPC, ISBN are all types of GTIN. In Google Shopping, submit the barcode number in the gtin field regardless of type.

EAN-13 is the 13-digit barcode format used on most UK and European products. UK EANs typically start with prefix 50.

UPC-A is the American 12-digit equivalent. You can convert UPC-A to EAN-13 by prepending a 0.

MPN (Manufacturer Part Number) is a manufacturer-assigned code — not a global identifier, just the code the manufacturer uses internally. Typically alphanumeric. Two manufacturers could assign the same MPN to different products.

When does Google Shopping require a GTIN?

• Products you buy from manufacturers or distributors and resell: almost always have GTINs
• Branded products you manufacture yourself: register GTINs with GS1 UK (from £119/year)
• Handmade, custom, or one-of-a-kind products: no GTIN — use identifier_exists: no
• Vintage or antique products: no GTIN — use identifier_exists: no

MPN as a fallback

If a product has no GTIN but has a manufacturer part number — common in automotive parts, electronics components — submit MPN + brand as the identifier combination. Google accepts this where MPN is the standard industry identifier. If you have an EAN, use it. MPN is a fallback, not a first choice.

The EAN checksum validation problem

EAN-13 barcodes include a check digit calculated from the first 12 digits. If your stored data has been corrupted — Excel treating the 13-digit number as scientific notation (5.05E+12), leading zeros stripped by a numeric database field — the checksum fails and Google rejects it as invalid.

Trajekt validates EAN-13 format and checksum before including in feed output, flagging invalid barcodes for review.

How much does GTIN coverage actually matter?

Products with correct GTINs consistently show higher impression share and better CTR than equivalent products without GTINs. Google uses GTINs to match products to its product knowledge graph — a database of millions of products with associated shopping signals. Products matched to this graph get additional ranking signals that unidentified products don't access. Improving GTIN coverage from 60% to 95% typically yields a meaningful increase in total Google Shopping impressions.