What is an MPN (Manufacturer Part Number)?

On a supplier's price sheet it shows up as "Mfr. ref.", "Part number" or "Model"; in Google Merchant Center, as the mpn attribute. It is the reference the manufacturer gives its product, which is why you only have it right if you copy it from them. It matters if you sell other brands' products: together with the brand and the GTIN, the MPN says exactly which item is on your product page, and when the product has no GTIN, Google asks for it.

How it works

Google defines it in one line: the manufacturer part number, a property that uniquely identifies the product to a given manufacturer.⁠^{[1]Google Search Central. Merchant listing (Product, Offer) structured data} The second half is the important one. Two different manufacturers can use the same reference for things that have nothing in common, so an MPN without its brand identifies nothing; with the brand, it does.

In Schema.org, mpn is the manufacturer part number of the product, or of the product an offer refers to. Its value is text, and the Product, Offer and Demand types can carry it.⁠^{[2]Schema.org (version 30.1, September 16, 2026). mpn} In the structured data for merchant listings, Google lists it among the recommended properties, next to the GTINs.⁠^{[1]Google Search Central. Merchant listing (Product, Offer) structured data}

In Merchant Center, the mpn attribute is required on every product that has no manufacturer-assigned GTIN, and optional on made-to-order goods such as art or handmade crafts. It takes 1 to 70 alphanumeric characters and maps to Schema.org's Product.mpn property.⁠^{[3]Google Merchant Center Help. MPN [mpn]}

Google's rules

The attribute's page in Merchant Center sets out how to fill it in:⁠^{[3]Google Merchant Center Help. MPN [mpn]}

• Use the MPN the manufacturer assigned. Unless you are the manufacturer, do not use a value you created.
• Submit it only if you are sure it is correct; when in doubt, leave it out.
• Each product gets its own correct MPN. In apparel, the sizes of one model can share one.
• For a bundle or a multipack: if the manufacturer created it, its own MPN; if you created it, the MPN of the main product.
• For a compatible or refurbished product, the MPN of whoever actually made it, not that of the original brand of the device it works with.
• Submit it together with the other identifiers, the brand and the GTIN.

When there is none

Some products have no identifiers: a custom-printed T-shirt, a piece of art, something handmade, an antique, or a book published before 1970. For those, Merchant Center has the identifier_exists attribute, set to "no" when the product has no GTIN, MPN or brand. Use it only if you are sure: a product marked this way that shows signs of having an identifier gets a warning.⁠^{[4]Google Merchant Center Help. Identifier exists [identifier_exists]}

In a store

Fictional example. A photography store sells four different items. What counts in each is who made it:⁠^{[3]Google Merchant Center Help. MPN [mpn]}⁠^{[4]Google Merchant Center Help. Identifier exists [identifier_exists]}

On the tripod's page, the product node in JSON-LD would carry the three references separately, each in its own property (the brand, the MPN and the GTIN are made up, and the GTIN uses the 952 prefix, which GS1 reserves for demos and examples):⁠^{[5]GS1. GS1 Company Prefix}

{
  "@context": "https://schema.org",
  "@type": "Product",
  "name": "TV-200 Travel Tripod",
  "brand": { "@type": "Brand", "name": "Fotomarca" },
  "mpn": "TV-200-BK",
  "sku": "STORE-0457",
  "gtin13": "9520000123451"
}

mpn and sku look different because they are not set by the same person: the first comes from the manufacturer, and the second, the SKU, is the store's internal reference.⁠^{[1]Google Search Central. Merchant listing (Product, Offer) structured data}

How to check it

1. Export the catalog and put the SKU and MPN columns side by side. If they match on every row for products you do not make yourself, the MPN column was filled with your own references.
2. Check a sample against the manufacturer's spec sheet or website: it is the only valid source of the MPN when you are not the maker.⁠^{[3]Google Merchant Center Help. MPN [mpn]}
3. Review the products with identifier_exists set to "no". If any has an MPN or a GTIN, it will get a warning.⁠^{[4]Google Merchant Center Help. Identifier exists [identifier_exists]}
4. Open the JSON-LD of a page and check that mpn says the same as the feed and that the brand sits in its own property.⁠^{[2]Schema.org (version 30.1, September 16, 2026). mpn}
5. On products with product variants, check that each one carries its correct MPN; in apparel, sizes can share it.⁠^{[3]Google Merchant Center Help. MPN [mpn]}

Related concept: SKU

The SKU and the MPN get confused because both are alphanumeric references and they often sit in neighboring columns. The difference is who sets them. The SKU is the merchant's own identifier for the product; the MPN is assigned by the manufacturer and identifies the product within their brand.⁠^{[1]Google Search Central. Merchant listing (Product, Offer) structured data} If you manufacture, they can match; if you resell, the MPN is the manufacturer's even when your SKU is something else. The third code, the number under the barcode, has its own entry: the EAN code.

To keep going, the structured data reading path lays out the rest of the terms, and the GTIN entry explains the barcode family the EAN belongs to.