In short. Google Merchant Center uses GTIN, MPN, and brand to identify products, with specific rules for variants and goods without assigned identifiers.

Definition: Product identifiers are catalogue fields that describe a product's identity: a Global Trade Item Number (GTIN), a Manufacturer Part Number (MPN), and its brand name. A GTIN identifies a trade item, while an MPN identifies a specific product within a manufacturer's range.

As of 17 October 2026, Google's product data specification groups gtin, mpn, and brand under product identifiers for Merchant Center, its product data submission service.

Key facts

Google's GTIN guidance recommends submitting a manufacturer-assigned GTIN when available and using the correct code for each colour or size variant.
Google's MPN guidance requires an MPN for products without a manufacturer-assigned GTIN, with exceptions for products without a clearly associated MPN and custom-made goods.
Google's brand guidance requires the brand for products with a clearly associated brand or manufacturer, including goods made by the merchant.
Google's identifier exists guidance provides identifier_exists=no for products without assigned identifiers. The value must be submitted in English.

Which value belongs in each field?

The GTIN attribute documentation accepts several numbering systems. The documentation lists UPC as a 12-digit code used in North America and EAN as a 13-digit code used in Europe. For books, Google specifies the ISBN-13 numbering format. The same guidance requires a correct check digit and excludes restricted and coupon ranges.

An MPN comes from the manufacturer. Google's MPN requirements say each variant typically has its own MPN, with an exception for apparel sizes, which often share one. A merchant reselling goods uses the manufacturer's assigned value.

The brand requirements call for the product brand shoppers generally recognise. For a compatible replacement product, the field contains the brand of the manufacturer that actually makes the replacement. A merchant that manufactures or privately labels a product can use its store name.

How do these fields appear in a feed?

A feed is a file containing product records submitted to Merchant Center. The following tab-separated fragment uses the brand, GTIN and MPN from Google's Chromecast example in its GTIN documentation:

brand	gtin	mpn
Google	7894892017139	H2G2-42

These columns form part of a product record. Merchant Center's product data specification also requires an id for each item and recommends retaining that value when updating data. This merchant item ID serves a separate role from the manufacturer identifiers.

Before submission, the GTIN guidance calls for checking the code's check digit and matching it to the exact variant. For example, a shirt offered in different colours needs the appropriate GTIN for each colour.

What if a product has no assigned identifiers?

Google's identifier exists documentation gives custom goods and vintage products as examples that may lack identifiers. For a product without assigned identifiers, a text feed can contain:

identifier_exists
no

The absence of a GTIN also has a specific alternative: Google's GTIN guidance calls for brand and MPN for store-brand or private-label goods without a GTIN. Its brand guidance tells merchants that manufacture and exclusively sell unbranded goods to submit the store name and choose a unique MPN.

FAQ

Can I invent a GTIN when one is missing?

Google's product data specification says to leave the field out when you are unsure of the value. It explicitly instructs merchants against guessing or making up a GTIN.

Does every product size need a different MPN?

Google's MPN documentation says variants typically have different MPNs, but apparel sizes often share one. Use the manufacturer's value for the variant you sell.

Sources

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