Definition
GTIN (Global Trade Item Number) is the globally unique number encoded in a product's barcode, licensed through GS1 to the brand owner, in one of four lengths: GTIN-8, GTIN-12 (the UPC used in North America), GTIN-13 (the EAN used elsewhere, and the form ISBNs take for books) and GTIN-14 for case packs. Merchant Center reads it from the gtin attribute to match a listing to Google's product catalogue, which makes the listing eligible for aggregated reviews, comparison placements and better query matching.
One feed row, with identifiers filled in correctly
- id
- shopify_CA_7712_40551
- title
- Stainless insulated bottle 750 ml, matte black
- brand
- Thermaline (an illustrative brand)
- gtin
- The 13 digit EAN printed beneath the bottle's barcode, entered without spaces, check digit intact
- mpn
- TL-750-MB
- identifier_exists
- Left at the default of yes, because a GTIN is assigned
- condition
- new
An illustrative row. A resold item keeps the manufacturer's GTIN, while a product the store makes itself with no barcode sets identifier_exists to no instead of inventing a number.
Why it matters
GTINs matter because Google uses them to understand what a product is. A listing with a valid GTIN is matched to Google's catalogue entry, so it can appear in comparison placements, inherit review counts and be shown for queries the title alone would not earn. Merchant Center flags products whose manufacturer-assigned GTIN is missing from the feed as limited in performance, which lowers how often they serve. Invalid values, such as a wrong check digit or a restricted prefix, disapprove the item outright. Beyond Google, the same number is what marketplaces, Meta catalogues and price comparison engines key on, so a store with clean GTINs in Shopify's barcode field or the WooCommerce GTIN field has done the identifier work once for every channel.
Where it goes wrong
- Entering the supplier's SKU or an internal code in the gtin field, which fails the check digit and disapproves the product for an invalid value
- Putting the same GTIN on every size or colour of a product, when each variant has its own barcode and each feed row needs the matching one
- Setting identifier_exists to no for a branded product that plainly has a barcode, which Google treats as a misrepresentation risk rather than a shortcut
- Reusing a number from a coupon or variable weight range, which Merchant Center rejects because those prefixes are reserved and never identify a retail product
- Spreadsheet imports that store the number as an integer and drop a leading zero, leaving eleven digits that never validate
Questions about GTIN
Do all products on Google Shopping need a GTIN?
No. Google requires the gtin attribute for products that have one assigned by the manufacturer, and treats it as missing when it is left out. Custom made goods, one-off pieces, vintage items and private label products that were never barcoded submit identifier_exists as no and are eligible without a GTIN. Brand and MPN together are the fallback for products that have a manufacturer part number but no barcode.
Where does a Shopify store enter GTINs?
In the Barcode field on each variant, which Shopify labels as ISBN, UPC, GTIN and so on. The Google and YouTube channel maps that field to gtin automatically. WooCommerce added a native GTIN, UPC, EAN or ISBN field on products and variations in version 9.2, and most feed plugins map it; older stores may hold the number in a custom field that needs mapping by hand.
How does a store get GTINs for its own products?
By licensing them from GS1, either a company prefix that covers a range of products or single GTINs one at a time, through the GS1 member organisation for the country the business is based in. Numbers bought from resellers outside GS1 may fail Merchant Center's ownership checks, so the licence should be in the brand's own name.