Fix missing GTIN warnings in Google Merchant Center (Shopify)
Typical Merchant Center message: Missing value [gtin] · Limited performance due to missing identifiers
Reviewed October 12, 2026 against Google’s published rules.
A GTIN is the manufacturer’s barcode number (UPC, EAN, ISBN or GTIN-14). Google uses it to match your offer to the right product. Missing or invalid identifiers can limit visibility or disapprove the product.
Do you need a GTIN?
If the product has a barcode assigned by its manufacturer — most branded products do — submit that exact GTIN. In Shopify it goes in each variant’s Barcode field.
If you make the product yourself, sell custom or handmade items, or the product never had a barcode, you do not need one. Set identifier_exists to no in your feed, and send brand and MPN where you have them.
Never invent a GTIN or reuse one from another product. Google checks the number and its check digit, and identifiers from restricted or coupon ranges are rejected.
How to fix it
- Find the manufacturer’s barcode on the packaging or from your supplier and enter it on the right variant.
- Check it has 8, 12, 13 or 14 digits and a valid check digit; do not drop leading zeros.
- Make sure two different products do not share the same GTIN.
- For your own products, send identifier_exists = no instead of an empty or made-up value.
Check your own catalog for these issues
FeedGuard checks GTIN length, check digits, restricted prefixes and repeated GTINs across items, and shows which products still need identifiers.
Google’s requirement: support.google.com/merchants/answer/6324461. FeedGuard checks your data against published rules; Google makes the final approval decision.
Independent guidance. Google’s current documentation and decisions control. FeedGuard is not affiliated with, endorsed by or sponsored by Google or Shopify, and this guide is not an official Google Help Center page.