You open Merchant Center and see “Limited performance due to missing value: GTIN [gtin]” next to a long list of products[6]. Or you sell your own branded goods and have no idea what number Google wants. Before you type anything into the feed, it helps to know exactly what each identifier is. Google’s own advice is to leave a GTIN out rather than guess one[1]. This guide covers the GTIN in Google Merchant Center and the attributes around it.
A GTIN (Global Trade Item Number) is the barcode number a manufacturer assigns to a product[1]. In your feed, you submit it in the “gtin” attribute when the product has one, and you add “brand” and “mpn” (manufacturer part number) to help Google match the product. The “identifier_exists” attribute tells Google whether a product has identifiers at all[4]. Never invent a GTIN, and don’t create your own MPN unless you’re the manufacturer[1][2].
What a GTIN is and which types exist
A GTIN is the number printed under a barcode. It identifies one specific product, so Google can recognise that your blue kettle and another seller’s identical blue kettle are the same item.
Google accepts these formats[1]:
- UPC (GTIN-12): 12 digits, used in North America.
- EAN (GTIN-13): 13 digits, used in Europe.
- JAN: 8 or 13 digits, used in Japan.
- ISBN: 13 digits, for books. If you only have an ISBN-10, convert it to the 13-digit version.
- ITF-14: 14 digits, used for multipacks.
Google recommends providing a GTIN for all products that have a manufacturer-assigned one[1]. It isn’t framed as a blanket requirement for every product, but missing or incorrect GTINs may limit your visibility. And if a product does have a GTIN and you don’t submit it, the product could be disapproved[1].
The GTIN rules to check
A GTIN can look correct and still break Google’s rules. Check these before you upload:
- The check digit (the final digit, calculated from the others) must be correct[1]. A typo in any digit usually breaks it.
- Don’t use restricted ranges, which start with 02, 04 or 2[1].
- Don’t use coupon ranges, which start with 05, 98 or 99[1].
- If you’re unsure, don’t provide a GTIN. Google says not to guess or make one up[1].
Watch out
A spreadsheet can quietly damage GTINs. Leading zeros disappear when a column is formatted as a number, and long values can turn into scientific notation. Format the GTIN column as text before you paste anything in, and open the file again afterwards to check it.
Where to find the right GTIN
Look at the packaging first, then the supplier’s price list or product data sheet. If you resell branded goods, ask the supplier or the brand directly. Whatever the source, it should be the number the manufacturer assigned[1]. Don’t pull numbers from a marketplace listing and assume they’re right. Another seller may have entered theirs wrongly.
MPN: the second identifier
The “mpn” attribute is the manufacturer part number. It’s the code a manufacturer uses to identify a product within its own range, often printed on a label or in the spec sheet. Google requires it for products that don’t have a manufacturer GTIN. It can be 1 to 70 characters long[2].
One rule matters most: don’t create your own MPN unless you’re the manufacturer[2]. If you’re a reseller and the supplier gives you only an internal SKU, that isn’t the manufacturer’s part number. Ask them what the real one is. If you can’t find one, leave it out rather than substitute something that looks plausible.
Brand: required more often than you’d think
The “brand” attribute is required for products with a clearly associated brand. It’s optional for movies, books, music and posters[3][5]. Use the brand name as the manufacturer uses it, not a category or a description.
Don’t fill the field with placeholders such as “N/A”, “Generic”, “No brand” or “Does not exist”[3]. If a product genuinely has no brand, leave the field empty.
What private-label sellers should do
If you make or commission your own products and sell them under your store name, you may have no manufacturer GTIN to submit. Google’s guidance is to use your store name as the brand and include an MPN of your choice, instead of setting identifier_exists to false[3]. This is the one case where you assign the MPN yourself, because the product is your own. Keep the MPN consistent for each product, and don’t reuse it across different items.
identifier_exists: what it actually does
The “identifier_exists” attribute tells Google whether a unique product identifier exists for the product. In feed files it accepts yes, true, no or false, in English. In the Merchant API only true and false are accepted. The default is yes, so if you leave it out, Google assumes identifiers exist[4][5].
Set it to no only when the product really has no identifiers. Google lists vintage items, antiques and books published before 1970 as examples of products that may have none[4]. A product whose GTIN you simply haven’t found yet is a different case, so ask the supplier first.
Good to know
Even when you set identifier_exists to no, Google still asks you to provide whichever identifiers you do have[4][5]. If such a product has a brand, for example, include it. Setting “no” doesn’t replace the identifiers you have.
Don’t set it to no just to clear a warning on a branded product that has a barcode. If the product has a GTIN, the fix is to submit that GTIN[1].
What to submit for each kind of product
- Branded product from a manufacturer or distributor: gtin from the manufacturer, brand and mpn if you have it[1][2][3].
- Branded product with no manufacturer GTIN: brand and the manufacturer’s mpn. Leave gtin blank[2][3].
- Private-label product: your store name as brand and an mpn of your choice, rather than identifier_exists set to false[3].
- Multipack: the 14-digit ITF-14 GTIN if the manufacturer assigned one to the multipack[1].
- Book: the 13-digit ISBN. Convert an ISBN-10 first[1]. Brand is optional[3][5].
- Vintage item, antique or pre-1970 book: these may have no identifiers. If so, set identifier_exists to no and still submit any identifiers you do have[4].
How to fix the “missing value GTIN” notice
Google’s help page for “Limited performance due to missing value: GTIN [gtin]” covers this issue[6]. One practical way to work through it is in three steps. First, diagnose. Open the list of affected products in Merchant Center and sort them into those that have a manufacturer GTIN and those that don’t. Second, fix the source. Add the real GTIN in your store platform’s barcode field or in a supplemental feed, so the number survives the next sync. Third, check. After the next feed fetch, look at the issue again and confirm the count is falling.
If the product has no GTIN, don’t add one. Provide the brand and the manufacturer’s mpn, and set identifier_exists to no only if the product genuinely has no identifiers, as described above[4]. If other disapprovals are also showing, this walkthrough on fixing them may help: https://oxfordimpulse.com/fix-products-not-showing-google-shopping/
Pre-submission checklist
If you’d rather have someone audit your feed attributes, Oxford Impulse covers this as part of its work with stores on Google Merchant Center: https://oxfordimpulse.com/google-merchant-center/
FAQs
What is a GTIN in Google Merchant Center?
It’s the number the manufacturer assigns to a product, usually shown under the barcode. You submit it in the “gtin” attribute so Google can identify exactly which product you’re selling[1].
Is a GTIN required for Google Shopping?
Google recommends providing a GTIN for all products that have a manufacturer-assigned one. If a product has one and you don’t submit it, the product could be disapproved, and missing or incorrect GTINs may limit visibility[1].
Where do you find a product’s GTIN?
Check the packaging, the supplier’s product data or the manufacturer directly. Use the number the manufacturer assigned[1], not one copied from another seller’s listing.
Can you make up a GTIN if you don’t have one?
What is an MPN in Google Merchant Center?
The MPN is the manufacturer part number, a code of 1 to 70 characters that identifies the product within the manufacturer’s range. It’s required for products without a manufacturer GTIN[2].
Can you create your own MPN?
What should you use as the brand for private-label products?
What does identifier_exists do?
What values does identifier_exists accept?
Which products can legitimately have no identifiers?
Google’s examples include vintage items, antiques and books published before 1970[4]. A product whose identifier is simply missing from your records is a different case, so ask your supplier first.
Sources
- Google Merchant Center Help: GTIN [gtin] support.google.com
- Google Merchant Center Help: MPN [mpn] support.google.com
- Google Merchant Center Help: Brand [brand] support.google.com
- Google Merchant Center Help: Identifier exists [identifier_exists] support.google.com
- Google Merchant Center Help: Product data specification support.google.com
- Google Merchant Center Help: How to fix: Limited performance due to missing value GTIN support.google.com
