You stare at the Google Merchant Center feed spec, see "gtin" required, and wonder whether the barcode on the box is the same thing as the SKU in your Shopify admin. You are not alone. GTIN is the single most misunderstood field in product feeds, and guessing wrong here gets your items paired with someone else's listing.
What you'll take away
- GTIN is not your SKU — the manufacturer assigns it, you do not.
- Formats differ by market — UPC, EAN, and ISBN are all valid GTIN structures.
- Never fabricate a number — an invented GTIN links your product to the wrong item.
- Check before submitting — packaging, manufacturer docs, and GS1 databases confirm the real identifier.
What exactly is a GTIN in Google Shopping?
A GTIN, or Global Trade Item Number, is a standardized identifier assigned by the manufacturer or a relevant standards organization to identify a specific product. Google Merchant Center uses it to match your feed item to a known product in its catalogue. When the identifier is correct, Google understands exactly which product you are selling and can show it to the right shoppers.
The term covers several barcode formats you may already have on your packaging. UPC is common in North America. EAN is the European equivalent. ISBN identifies books. All of these are valid GTINs in Google's product data specification, just encoded at different lengths.
Google's product data specification accepts these formats because the underlying numbering system is managed by GS1, the global standards body. The digits encode a company prefix, an item reference, and a check digit that validates the whole string. That structure is why a random number will never pass as a real GTIN for long.
How does GTIN differ from SKU and MPN?
GTIN and SKU serve entirely different purposes, and confusing them is the most common feed mistake we see. A SKU, or Stock Keeping Unit, is an internal code created by the merchant to track inventory in their own system. A GTIN is assigned externally by the manufacturer or brand owner. Google Merchant Center wants both when available, but they go in separate feed fields.
| Identifier | Who assigns it | Feed field | Scope |
|---|---|---|---|
| GTIN | Manufacturer / GS1 | gtin | Global |
| MPN | Manufacturer | mpn | Global |
| SKU | Merchant | id | Internal only |
MPN, or Manufacturer Part Number, sits between the two. The manufacturer assigns it, like the GTIN, but it is not a barcode. Google uses MPN as a secondary identifier when no valid GTIN exists, which is common for automotive parts, custom goods, and niche electronics.
Why does Google disapprove items for wrong identifiers?
Google disapproves items with incorrect GTINs because an inaccurate identifier associates your listing with the wrong product, which misleads shoppers and undermines trust in Shopping ads. The disapproval is not a formatting complaint. It is a signal that Google cannot confidently say what you are selling.
Did you know that GS1 maintains the only legitimate source of company prefixes for GTINs, and Google can verify your identifier against the GS1 database in real time?
When you submit a GTIN that belongs to a different product, Google may match your ad to that product's reviews, images, and price comparisons. Shoppers who click through see something that does not match your page. That mismatch triggers a policy violation, and the item goes offline.
A wrong number is worse than no number
Leaving the GTIN field empty is acceptable for products that genuinely do not have one. Filling it with a fabricated or borrowed number will get the item disapproved and can flag your entire Merchant Center account for a data quality review.
Should I submit a GTIN if I am not sure it is correct?
No. Do not submit a GTIN unless you have verified it against the manufacturer's packaging or a reliable product record. Google's policy is explicit on this point: items that have a valid GTIN must include it, but items without one should leave the field empty rather than guess.
The temptation is real. Merchants see the feed requirement, panic, and paste a number from a similar product or generate one that fits the digit count. Google can validate GTINs against the GS1 database, so a fabricated number will fail the check-digit calculation at minimum and trigger a full mismatch at worst.
Verify a GTIN in four steps
Which products are exempt from the GTIN requirement?
Google Merchant Center does not require a GTIN for every product. Custom goods, handmade items, and private-label products that you manufacture yourself typically do not have one. In those cases, you set the identifier_exists field to no and provide a brand plus an MPN if you have one.
Before
identifier_exists = yes, gtin = 0000000000016
After
identifier_exists = no, brand = Your Brand, mpin = YB-001
The "before" example shows a fabricated GTIN with a valid check digit but no real product behind it. Google will catch this because the prefix is not registered to any company. The "after" example is honest and compliant.
How to audit your existing feed for GTIN errors
Run a GTIN audit before Google runs one for you. Export your feed, isolate the gtin column, and check every value against three tests. Every GTIN you submit should be traceable to a real product through its manufacturer or brand owner.
- Length check — confirm each value is 8, 12, 13, or 14 digits. Anything else is malformed.
- Check-digit validation — run the GS1 algorithm to confirm the final digit matches the calculated value.
- Company prefix lookup — verify the leading digits correspond to a registered GS1 company prefix.
If any value fails these tests, remove it from the feed and investigate the source of the error before resubmitting.
Common questions
Is a GTIN the same as a barcode number?
Yes, a GTIN is the number encoded in the barcode printed on retail packaging. UPC, EAN, and ISBN are all formats of GTIN that appear as barcodes on different products in different markets. You can read the digits directly from the packaging and submit them in the gtin field of your Google Merchant Center feed.
Do I need a GTIN for custom or handmade products?
No, custom and handmade products typically do not have a GTIN because they are not mass-produced items tracked through GS1. Set identifier_exists to no in your feed and provide your brand name plus an MPN if you have assigned one internally. Google will not require a GTIN for these product types.
Can I use my SKU as a GTIN?
No, a SKU is an internal inventory code that you create and manage. A GTIN is assigned by the manufacturer or a standards organization and registered with GS1. Submitting a SKU in the GTIN field will fail Google's validation checks because the number does not correspond to a real GS1 company prefix.
What happens if I submit a wrong GTIN?
Google will disapprove the affected item and may flag your Merchant Center account for a broader data quality review. The wrong GTIN can cause Google to associate your product with a different item's images, reviews, and price data, which creates a misleading experience for shoppers and violates the Shopping ads policy.
Where do I find the GTIN for a product I resell?
Check the barcode printed on the product packaging, which is the authoritative source. You can also review the manufacturer's product specification sheet or search the number in the GS1 GEPIR database to confirm which company it belongs to. Never copy a GTIN from another merchant's listing because their feed may already contain an error.
GTINs exist so that Google, the manufacturer, and your store all refer to the same product by the same number. Submit the one on the box. Leave the field empty when there is no box. The cost of a wrong number is always higher than the cost of a blank one.