MPN, submitted as <g:mpn> in Google Merchant Center feeds and mpn in Meta Catalog, is the manufacturer-assigned part number used to identify a specific product model -- an alphanumeric string such as AX-NC200-BLK that's unique within that manufacturer's own catalog, though not globally unique the way a GTIN is. It exists as the fallback identifier for products that were never assigned a GTIN by their manufacturer.

Why It Matters

When a product genuinely has no GTIN, Google and Meta both require brand and mpn to be submitted together as the substitute identity pair, and without both fields present the listing is treated as having no identifiers at all, which suppresses it from richer Shopping formats and product-matching features. Because mpn alone is only unique within one manufacturer, submitting an mpn without a matching brand value is functionally useless for catalog matching, so the two fields have to be maintained as a linked unit rather than independently. Retailers sourcing private-label goods, refurbished electronics, or made-to-order items lean on this pair constantly, since a real, manufacturer-issued GTIN often doesn't exist for that class of product.

How It Works

Google only accepts mpn as a valid identifier when identifier_exists is not set to false and no gtin is available; if both gtin and mpn are present, Google prioritizes gtin for catalog matching and treats mpn as supplementary data rather than a competing identifier. There's no fixed format Google validates against beyond a reasonable character length, since manufacturers use wildly different part-numbering conventions, but Google does flag obviously placeholder values, like a repeated SKU used across unrelated products, as invalid. Meta Catalog applies the same logic: mpn plus brand is accepted as a fallback identifier set when gtin is absent, following Meta's own identifier_exists flag. Merchants migrating from a feed that conflated internal SKUs with true manufacturer part numbers often trigger a fresh round of identifier errors the next time Google re-validates the catalog, a scenario covered directly in Fix Common GTIN and Product Identifier Errors in Your Shopping Feed.

Example

<item>
  <g:id>SKU-88420</g:id>
  <title>Refurbished Espresso Machine - Silver</title>
  <link>https://example-shop.com/products/espresso-machine-silver</link>
  <g:price>249.00 USD</g:price>
  <g:identifier_exists>false</g:identifier_exists>
  <g:brand>Lucera</g:brand>
  <g:mpn>LC-ESP-2200-SLV</g:mpn>
</item>

Related Concepts

MPN only functions as an identifier alongside brand, since a part number without the manufacturer name attached can't be matched to anything, and it serves as the direct substitute for GTIN whenever no globally issued code exists for a product. Feed teams should also keep mpn distinct from an internal SKU, which tracks a different, warehouse-specific identity and shouldn't be repurposed as a manufacturer part number just because both fields happen to be alphanumeric strings. Getting this pairing right the first time saves a second cleanup pass later, since brand and mpn tend to be entered manually far more often than gtin, which is usually pulled straight from supplier data.