GTINs, SKUs and brand: why AI shopping agents care about barcodes
Short version: A GTIN (the number under a barcode: UPC, EAN or ISBN) tells an agent exactly which product you sell, so it can compare you with other stores selling the same thing. In Shopify it's the Barcode field on each variant. If yours are blank, agents have to guess.
Three identifiers, three jobs
- GTIN (UPC in North America, EAN elsewhere, ISBN for books): a global number for one exact product. The same shoe in the same size and color has the same GTIN in every store.
- SKU: your own internal code. Useful to you, meaningless to anyone else.
- Brand (Shopify's Vendor field): who makes it. Agents combine brand with GTIN or a model number to be sure.
Why agents care
A shopper asks for "the best price on these exact headphones." The agent finds the same product in several stores. With a GTIN it knows they're identical and can compare price, stock and shipping. Without one it has to match on titles, which is how you lose to a store with worse prices but cleaner data. Google Merchant Center has long required GTINs for products that have one, for the same reason.
Where they live in Shopify
Each variant has a Barcode (ISBN, UPC, GTIN, etc.) field on the product page in Shopify admin. Fill it in per variant, since every size and color has its own GTIN. Bulk-editing or a product CSV import is faster for big catalogs.
Then check your product page markup. Agents and search engines read the Product structured data your theme outputs, and identifiers only help if the theme includes them there.
Products without a GTIN
Handmade, custom and private-label products often don't have one, and that's fine. Don't invent numbers. Make sure brand and a stable model or part number (MPN) are filled in instead.
Questions
Where do I add a GTIN in Shopify?
In the Barcode field on each product variant in Shopify admin. Each size and color usually has its own GTIN.
Can I make up GTINs for my own products?
No. GTINs are issued by GS1. If your products don't have them, leave the field blank and fill in brand and a model number instead.
Is a SKU the same as a GTIN?
No. A SKU is your internal code. A GTIN is a global number that means the same product in every store.