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Unique Product Identifiers

Product and catalog managementBasic Level

Unique product identifiers are the codes that identify a product across channels: the GTIN, and the brand plus MPN. Your own SKU identifies it only inside your business.

What is Unique Product Identifiers?

Unique product identifiers are the codes that tell a channel exactly which product you sell: the GTIN (such as a UPC, EAN or ISBN), the manufacturer part number (MPN) and the brand. Your own SKU is an identifier too, but only inside your business. Google Shopping and marketplaces use these identifiers to match your offer to the right product in their catalog, group it with other sellers and show it for the right searches. The GTIN is unique worldwide. An MPN is only unique together with the brand, so channels ask for both. A marketplace can add its own ID, such as the Amazon ASIN. Products with none of these, such as custom-made items, use identifier_exists set to no in Google Merchant Center. You can check the GTIN and brand of a product with the free Google Shopping feed checker. Read more about the GTIN, MPN, SKU and ASIN.

Why Unique Product Identifiers matters for e-commerce

Identifiers decide whether a channel recognizes your product. Google reported conversion increases of up to 20% for merchants who added correct GTINs (Google, 2017). Missing or wrong identifiers lead to disapproved products, offers attached to the wrong catalog page and duplicate listings. Identifiers also connect your own systems. The SKU links orders, stock and product data, while the GTIN and brand plus MPN link the same product to every channel. Keeping them as separate, validated fields avoids the classic mistake of sending a SKU where a channel expects a GTIN.

Examples of Unique Product Identifiers

  • 1Product: Running shoe, size 42, GTIN: 8712345678906, Brand: Example Sports, MPN: RS-42-BLK, SKU: SHOE-RS-42-BLK
  • 2Product: Paperback book, GTIN: the ISBN-13 printed on the back, Brand: the publisher, MPN: not needed
  • 3Product: Replacement printer part, GTIN: none, Brand: the manufacturer, MPN: the manufacturer's part number
  • 4Product: Custom engraved ring, GTIN: none, MPN: none, Google: identifier_exists = no

How WISEPIM Helps

  • Keep the GTIN, MPN, brand and SKU as separate attributes per variant in WISEPIM.
  • WISEPIM validates the GTIN check digit, and Quality Guard rules flag products that miss an identifier.
  • Channel Readiness shows per channel which products are not ready because an identifier is missing.

Common mistakes with Unique Product Identifiers

  • Sending your own SKU in the GTIN or MPN field.
  • Sending an MPN without the brand.
  • Giving several variants the same GTIN. Every size and color needs its own.
  • Setting identifier_exists to no for branded products that do have a GTIN.

Tips for Unique Product Identifiers

  • Store each identifier in its own field, never combined in one text field.
  • Take the GTIN and MPN from the manufacturer, not from another shop's listing.
  • Give every variant its own GTIN and SKU.
  • Check identifiers before you send a feed, not after a channel rejects it.

Trends around Unique Product Identifiers

  • Channels match more offers automatically by GTIN, so a wrong identifier puts your offer on the wrong product page.
  • AI shopping assistants use identifiers to tell near-identical products apart.
  • GS1 Digital Link puts the GTIN in a QR code that links to product information.

Tools for Unique Product Identifiers

  • Google Merchant Center: the gtin, mpn, brand and identifier_exists attributes
  • GS1: issues GTINs and runs the Verified by GS1 lookup
  • WISEPIM: identifier attributes, GTIN check digit validation and Quality Guard rules

Related Terms

Attribute GroupAttributizationCategory ManagementCircular Product IdentityCountry of OriginDigital Catalog

Also Known As

Product identifiersProduct IDsUPIs

Frequently Asked Questions

A unique product identifier is a code that tells a channel exactly which product you sell. The main ones are the GTIN, and the brand plus MPN for products without a GTIN.

Google asks for the GTIN for products that have one, and the brand plus MPN for products without a GTIN. For products with no GTIN and no MPN, such as custom-made items, you set identifier_exists to no.

A SKU identifies the product inside your own business, but channels do not use it to recognize the product. Two shops use different SKUs for the same item, so channels rely on the GTIN, brand and MPN.

A GTIN is unique worldwide and comes from GS1. An MPN comes from the manufacturer and is only unique together with the brand.

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