Concept
Product identifiers
Also called unique product identifiers, UPI, and GTIN, MPN and brand.
Product identifiers are the values that let a sales channel recognise that your listing and someone else's describe the same physical product: a GTIN, or a manufacturer part number together with a brand. They matter because a channel that can identify a product can attach reviews, specifications and competing offers to it, and one that cannot has to treat your listing as an unknown object.
Frequently asked questions
What are unique product identifiers?
The values that identify a product independently of who is selling it. In practice that means a GTIN, which is the barcode number assigned by the manufacturer, or the combination of a manufacturer part number and a brand where no GTIN exists.
Why do channels care about product identifiers?
Identification lets the channel attach reviews, specifications and competing offers to the same product, and place your offer among them. Without an identifier your listing is an unknown object that has to be matched on text alone, which is far less reliable.
What is the difference between GTIN, MPN and SKU?
A GTIN is globally unique and identifies the product no matter who sells it. An MPN is assigned by the manufacturer and is only unique within that manufacturer, which is why it needs a brand alongside it. A SKU is a code you invent for your own stock control and means nothing to anyone else.
What if my products have no identifiers at all?
Declare it, by setting identifier_exists to no. That is the correct handling for custom, handmade, vintage and own-brand goods with no manufacturer-assigned identifier. It is not a way to suppress warnings on products that do have barcodes you have not entered.
Related attributes
- gtin The gtin attribute is the globally unique barcode number a manufacturer assigns to a product, covering UPC, EAN, JAN and ISBN formats. Channels use it to match an item against the same product sold elsewhere, and on Shopify it comes from the variant's barcode field, which is optional in the admin and therefore frequently empty.
- mpn The mpn attribute is the part number a manufacturer uses to identify a product in its own catalogue, and it serves as the fallback identifier when an item has no GTIN. Unlike a GTIN it is only unique within one manufacturer, so it is meaningless to a channel unless the brand attribute is supplied alongside it.
- brand The brand attribute is the name of the brand a product belongs to, and it is what makes a manufacturer part number meaningful and a listing eligible for brand-based matching. On Shopify it maps most often from the vendor field, which is unreliable because merchants commonly use vendor to record a supplier or distributor rather than the consumer-facing brand.
- identifier_exists The identifier_exists attribute is an explicit declaration that a product has no manufacturer-assigned identifiers, set to no when a GTIN, MPN and brand genuinely do not exist for the item. It is a statement about the product, not a way to silence identifier warnings, and channels treat misuse as a data quality problem rather than a resolution.
Related errors
- Missing value: GTIN The "Missing value: GTIN" issue means a channel believes a product has a manufacturer-assigned barcode but the feed did not supply one. On Shopify it almost always traces back to the variant barcode field, which is optional in the admin and therefore left empty across large parts of most catalogues.
- Invalid value: GTIN The "Invalid value: GTIN" error means the feed supplied a value in the gtin attribute that is not a structurally valid Global Trade Item Number. Unlike a missing GTIN this is usually a disapproval rather than a warning, because a wrong identifier matches the item to the wrong product rather than to none.
- Missing value: brand The "Missing value: brand" issue means a channel expects a brand name for a product and the feed did not supply one, or supplied a placeholder it treats as empty. On Shopify it usually means the vendor field is blank, or holds a supplier or internal category rather than the brand a shopper would recognise.
Related concepts
Channels this applies to
Primary sources
Channel specifications change. These are the official documents this page is based on.