MPN

MPN vs GTIN

A GTIN (UPC, EAN, ISBN) is a global barcode number recognized across the whole supply chain. An MPN is narrower: the part number the manufacturer assigned to that specific product or variant. Google treats them as two routes to the same goal, matching your listing to a real, known product. If an item has a manufacturer-assigned GTIN, submit that. If it has none, the mpn attribute becomes required for the product to be approved. Custom-made goods with no clear part number (art, handmade items, novelty products, custom apparel) are exempt.

Rules that trip merchants up:

• Values are strings, 1 to 70 characters, and single-valued (no repeated field).
• Each product variant usually carries its own MPN. Google notes one exception: different sizes of the same apparel product often share a single MPN, so submit the correct value rather than assuming every line needs a different one.
• Use the manufacturer’s real value. Do not invent one or reuse an internal SKU. Google’s guidance is explicit: “When in doubt do not provide an MPN (for example, do not guess or make up a value).”

The same identifier belongs in your on-page structured data. Schema.org exposes mpn on Product and Offer, so a product page can carry:

"mpn": "GO12345OG"

Keeping the schema value identical to the feed value keeps Merchant Center, structured data, and the visible page consistent, which is what product matching rewards.