GTIN, MPN and brand: product identifiers in Merchant Center
The complete guide to Google Shopping product identifiers, when GTIN is required, valid GTIN formats and check digits, MPN + brand fallback rules, and identifier_exists.
Google uses three identifiers to work out exactly which product you're selling: GTIN (the barcode number), MPN (the manufacturer's part number) and brand. If your product has a barcode, Google wants it, products with correct GTINs get matched to Google's catalog, show in more places, and convert better. Fake or recycled GTINs get you disapproved.
The three identifiers
| Attribute | What it is | Example |
|---|---|---|
gtin |
Global Trade Item Number: the barcode number (UPC, EAN, JAN, ISBN, ITF-14) | 00012345678905 |
mpn |
Manufacturer Part Number: the maker's own model identifier | GO-2210-BLK |
brand |
The brand consumers know the product by | Nike |
Google uses these to match your offer to a catalog entry it already understands: pooling reviews, spec data and demand signals across every merchant selling the same item. Matched products are eligible for richer placements and typically see meaningfully higher click-through.
What's required when
- Product has a GTIN (any product sold with a barcode): submit
gtin+brand. This is not optional: knowingly omitting an existing GTIN limits performance, and wrong GTINs cause disapprovals. - Product has no GTIN but has a manufacturer (e.g. OEM parts): submit
mpn+brand. - Product genuinely has no identifiers (handmade, custom, vintage, own-brand without barcodes): submit
identifier_exists: false. Brand may still apply.
Deep dive GTIN formats and validation
Valid GTIN lengths are 8, 12, 13 and 14 digits (GTIN-8/EAN-8, GTIN-12/UPC-A, GTIN-13/EAN-13, GTIN-14/ITF-14). ISBNs (books) are valid as 13-digit GTINs when they start 978/979. Validation rules Google applies:
- Check digit: the final digit is a modulo-10 checksum of the preceding digits. A GTIN that fails the check digit is rejected outright. This catches most typos and most invented numbers.
- Prefix legitimacy: the leading digits encode the GS1 member prefix. Ranges that are reserved, retired (like the 04 range used internally by some retailers), or belong to a different brand's registered prefix will flag "incorrect identifier" even when the check digit passes.
- Restricted prefixes: numbers beginning
2(variable-weight in-store),02, and04ranges are in-store ranges and not valid for online listing. - Coupon prefixes (
98–99) are invalid for products. - Leading zeros matter for storage but not identity:
0012345678905and12345678905refer to the same GTIN-12; feeds should submit the number exactly as printed and let normalisation handle padding.
The classic failure mode at catalog scale: a bulk import maps SKU → gtin, thousands of products fail check-digit validation, and the account picks up an "incorrect product identifiers" warning that suppresses far more than the affected items. Validate before you submit, not after Diagnostics lights up.
identifier_exists: the escape hatch, and its misuse
identifier_exists: false tells Google "this product legitimately has no GTIN/MPN". Used honestly, it's exactly right for handmade and custom goods. Used to dodge the GTIN requirement on products that do have barcodes, it's a misrepresentation risk: Google cross-references your titles, brands and images against its catalog, and a branded product claiming to have no identifier is an easy flag.
Why this is worth doing properly
Identifier-complete products are the raw material for everything else: catalog matching, competitive placements, "popular product" surfaces and reliable disapproval-free serving. In /tools, identifier coverage is the heaviest-weighted input to your Feed Health Score, and the GTIN enrichment workflow can fill gaps by matching your products against external barcode databases: filling only where a confident match exists, and telling you which products still need a human answer.
Frequently asked questions
My products are handmade and have no barcode. What do I submit?
Set identifier_exists to false (called "no" in some interfaces) and submit brand where one genuinely exists. Don't invent a GTIN and don't submit your SKU as an MPN unless it truly is the manufacturer part number, for genuinely identifier-less products, identifier_exists false is the correct and safe answer.
Can I reuse one GTIN across colour variants?
No. Each sellable variant with its own barcode gets its own GTIN. Reusing one GTIN across variants is one of the most common causes of "incorrect product identifier" disapprovals.
Where do I find GTINs for products I resell?
The manufacturer or distributor is the source of truth, it's the number under the barcode on the packaging. For catalog-scale gap-filling, /tools can match products against external barcode databases and fill missing GTINs where a confident match exists.