When Google Merchant Center reports a missing GTIN, the cause in Shopify is almost always one empty field: the barcode of each variant. Shopify's Google integration sends this value as the GTIN. The fix: enter the real GTIN for every variant, taken from the packaging or from the manufacturer. If a product has no GTIN, for example handmade items or private labels without a GS1 number, mark it correctly for Google instead of entering a made-up barcode.
What a GTIN is and why Google wants it
The GTIN (Global Trade Item Number) is the globally unique item number of a product. In Europe you usually see it as a 13-digit EAN, in the US as a 12-digit UPC. Books have an ISBN, which also counts as a GTIN.
Google uses the GTIN to match your offer to a known product. Without that match, Google has a harder time comparing your product with other offers. For branded goods where the manufacturer assigned a GTIN, Google explicitly requires it. If it is missing there, the product gets limited or disapproved.
AI assistants like ChatGPT also work better with unique identifiers. A GTIN makes clear exactly which product is meant.
The most common causes
- Empty barcode field: the product was created without a barcode, often during a quick import or when duplicating.
- Only one variant filled in: every size and color has its own GTIN. If only variant 1 has a barcode, the others are missing.
- Wrong format: spaces, hyphens, too few digits or a wrong check digit. Google reports this as an invalid GTIN.
- Internal number in the barcode field: your own item number belongs in the SKU field, not the barcode.
- No GTIN exists, but it is not marked: Google has a dedicated way to handle products without GTINs. If you don't use it, Google only sees a gap.
- Missing brand: Google checks GTIN, brand and manufacturer part number (MPN) together. In Shopify, the brand usually comes from the Vendor field.
Step by step: adding the GTIN in Shopify
- In Shopify admin, open Products and select the affected product.
- If the product has variants, click the individual variant. Without variants, the fields are directly in the product's inventory section.
- Enter the number in the Barcode (ISBN, UPC, GTIN, etc.) field without spaces or special characters.
- Check that Vendor holds the real brand name, not your shop name, if you sell other brands.
- Save and repeat for all variants.
- Wait for the next sync with Merchant Center. It can take a few hours to a few days until the issue disappears.
For many products the bulk editor is faster: select several products in the product list, choose Edit and add the Barcode column. Alternatively, export the products as CSV, fill the Variant Barcode column and import the file again. When editing in Excel, make sure long numbers are not turned into scientific notation. Format the column as text first.
Where to get the right GTIN
| Situation | Source of the GTIN |
|---|---|
| You sell branded goods | Barcode on packaging or label, delivery note, price list or manufacturer data sheet |
| You buy from a wholesaler | The wholesaler's item master data, often as CSV or in the dealer portal |
| You produce yourself and want GTINs | Apply for your own numbers via GS1 (paid) |
| Handmade, one-of-a-kind, custom | No GTIN needed, but mark it correctly (see below) |
Don't buy cheap GTINs from resellers without a GS1 license. Google checks GTINs against GS1 data, and numbers registered to someone else can show up as invalid or mismatched.
If your product has no GTIN
Not every product needs a GTIN. Typical cases are handmade single pieces, made-to-order goods, vintage items and private labels that never applied for a GTIN.
For these products, Google's product data specification has the attribute identifier_exists. Set to no, it tells Google that no product identifier exists, so no GTIN is expected. How you set it depends on how your products reach Merchant Center. Shopify's Google integration and feed apps usually offer a per-product setting or a rule. In Merchant Center itself you can also set the attribute with feed rules.
Important: don't set identifier_exists to no just to get rid of an error. If the manufacturer assigned a GTIN, Google often notices, and the product stays limited.
Finding GTIN errors in Merchant Center
In Merchant Center, the product overview shows which items have issues. Filter by the missing or invalid GTIN issue. You get a list of affected products that you can download as a spreadsheet. Google renames menus from time to time, so look for the area for product issues or diagnostics.
Compare the list with your Shopify export. You will quickly see whether only single variants are missing or whole products.
Checklist: keeping GTINs clean
- Every variant has its own GTIN in the barcode field.
- Digits only, 8, 12, 13 or 14 digits, no spaces.
- The check digit is correct (many online calculators verify this).
- Internal numbers are in the SKU field, not the barcode.
- The Vendor field holds the real brand.
- Products without GTIN are marked with
identifier_exists = no. - After saving: wait for the sync and check Merchant Center again.
Faster with Heartly
Heartly shows a visibility score for Google Shopping and AI assistants for every product and lists missing or invalid GTINs per variant. With the "Fix now" assistant (Beta, Shopify, paid plan) you enter GTINs directly, scan the barcode with your phone or look it up. You review every change before it is saved and can undo it for 30 days. Missing SKUs can be filled the same way.
Frequently asked questions
Is the GTIN the same as the EAN?
Almost. EAN-13 is one form of GTIN. GTIN is the umbrella term that also covers UPC (12 digits), EAN-8 and GTIN-14.
Can I use my SKU as the GTIN?
No. The SKU is your internal number and not globally unique. Google does not recognize it as a GTIN and reports it as invalid.
How long until the error disappears?
After saving in Shopify, the change has to reach Merchant Center and be checked again. Expect a few hours to a few days.
Do private labels really need GTINs?
No. Without a GTIN you can submit products with brand and MPN, or with identifier_exists = no. If you plan to sell through marketplaces or retail, your own GS1 numbers are still worth it.
Check your catalog
Want to know how many of your products are affected right now? The free visibility check works without installing anything. If you want to close the gaps directly in Shopify, Heartly is in the Shopify App Store ($19 per month, 14-day free trial).