How to fix invalid GTINs in Shopify

What it means

Most invalid GTINs in Shopify stores aren't made-up numbers. They're real barcodes damaged on the way in: a spreadsheet dropped a leading zero, a digit was mistyped, or the field was used for something that isn't a GTIN at all, such as a SKU or a store's own in-house code.

Example diagnosis

Four variants of one store, pasted into the GTIN checker

4006381333932   ✗ Wrong check digit   correct: 4006381333931
42100005264     ✗ Wrong length        restored: 042100005264
TSHIRT-BLK-M    ✗ Not a number        (a SKU in the barcode field)
2001234567893   ✗ Restricted range    prefix 2: in-store numbering

Line 1 has the right length but the last digit doesn't match the check digit computed from the others, so one digit was mistyped. If the first twelve digits match the packaging, the GTIN ends in 1.

Line 2 is a 12-digit UPC that lost its leading zero when the product CSV was opened in a spreadsheet. Restored to 12 digits, it validates.

Line 3 is the variant's SKU typed into the barcode field. Line 4 passes the check digit but starts with 2, a range Google lists as restricted: it's for a shop's internal numbering or weighed goods, not a product identifier.

Symptoms

• Merchant Center's product list shows items under Needs attention with a GTIN issue, such as an invalid or incorrect value for gtin.
• Barcodes in your product export have 11 digits, letters or dashes, or start with 2, 02 or 04.
• The same barcode appears on several variants that are different products, often because a template value was copied across.
• Products you resell from a known brand show little or no Shopping traffic while similar products do.

How to fix it in Shopify

1. Find the bad codes. Export products from Shopify admin (Products → Export) and paste the variant barcode column into the free GTIN checker. It lists every code that fails, with the correct check digit where one digit is wrong.
2. Get the real number. Take the GTIN from the packaging, the manufacturer's product data or, for your own brand, your GS1 record. Don't guess a corrected digit unless the rest of the number matches the source.
3. Correct it in Shopify. Open the product, open the variant and edit its barcode. In the current product page the barcode sits under Inventory, where you choose the type (GTIN, UPC, EAN or ISBN) before entering the number.
4. Clear what isn't a GTIN. Remove SKUs, internal codes and restricted-range numbers from the barcode field. Keep SKUs in the SKU field.
5. Handle products that have no GTIN. For custom, handmade or own-brand products without one, leave the barcode empty and make sure your feed sends brand and MPN, or identifier_exists set to no, as Google's identifier guidance describes.
6. Fix many at once. For more than a few variants, correct the barcode column in the product CSV, format it as text so zeros survive, and import it back with the overwrite option.
7. Let Merchant Center re-check. Your feed app sends the new values on its next sync; the item issue clears once Google processes the updated product.

Caveats and when it applies

• A code that passes the checker is well-formed, not necessarily yours: the checker can't tell whether a valid GTIN belongs to this product. Only the manufacturer or GS1 can.
• The GS1 prefix shows which GS1 member organisation issued the company prefix, not where the product was made.
• If you sell other brands' products, they almost always have a GTIN. Google asks for it when one exists; leaving it out of a product that has one is a separate issue from an invalid one.
• Fixing the barcode in Shopify fixes your feed. If your theme also publishes gtin in the product page's structured data, check that it reads the same field, so the page and the feed agree.

Official documentation

• Google: GTIN [gtin] attribute
• Google: About unique product identifiers
• Google: Identifier exists [identifier_exists]
• Shopify: Product details page (SKUs and barcodes)
• Shopify: Importing and exporting products

The audit checks behind this guide

Related fixes

• Missing Google Shopping Product Attributes in Shopify
• Missing Product Schema in Shopify: How to Fix It
• Every check in a catalog audit