GTIN, MPN and SKU: whose number is each, and who may create it
A GTIN is the manufacturer’s barcode number, so only the brand owner creates it and everyone else copies it exactly. An MPN is the manufacturer’s part number, and Google says not to invent one unless you are the manufacturer. A SKU is yours: it is your internal code, and in a Google feed it usually goes in the id attribute. For handmade or one-of-a-kind products with no manufacturer codes, you set identifier_exists to no instead of making numbers up.
What this comes down to
- The GTIN belongs to the manufacturer; copy it from the product or the supplier, and never generate or guess one.
- The MPN also belongs to the manufacturer, and Google requires it only when a product has no GTIN.
- Your SKU is your own code, and in a Google feed it usually becomes the product id, up to 50 characters.
- For custom, handmade or vintage goods with no manufacturer codes, set identifier_exists to no rather than inventing values.
Three numbers, three owners
| Identifier | Whose number | In a Google feed |
|---|---|---|
| GTIN (the barcode number) | The brand owner or manufacturer | gtin: strongly recommended when one exists |
| MPN (part number) | The manufacturer | mpn: required only if there is no GTIN |
| SKU (stock code) | You, the seller | Usually the id, up to 50 characters |
Only one of these numbers is yours to make up.
GTIN: copy it, never create it
The GTIN is the number under the barcode. It comes in several lengths depending on where and what the product is:
- UPC, 12 digits, used mainly in North America
- EAN, 13 digits, used mainly in Europe
- JAN, 8 or 13 digits, used in Japan
- ISBN, 13 digits, for books
- ITF-14, 14 digits, for multipacks
Brand owners get their GTIN range from GS1, the standards organisation that issues barcode numbers. Everyone else copies the number from the product or the supplier. Google is blunt about the rest: Only provide a GTIN if you’re sure it’s correct. When in doubt don’t provide a GTIN.
And: Don’t guess or make up a value.
If you sell your own brand and want GTINs, they come from GS1 in your country, not from a random-number generator.
MPN: the manufacturer’s part number
The MPN identifies a product within one manufacturer’s range. Google’s rule mirrors the GTIN rule: Use the MPN assigned by the manufacturer. Unless you’re the manufacturer, don’t use a value that you’ve created.
It can be 1 to 70 characters. You need it only when the product has no GTIN; with a GTIN, it is optional.
SKU: the one that is yours
A SKU is your own stock code. You invent it, you own it, and nobody outside your business needs to recognise it. In a Google feed, the natural home for it is the id attribute, which identifies the product within your feed and can be up to 50 characters.
The one rule that matters: keep the id stable. It is how Google connects today’s product to yesterday’s, and how a supplemental data source finds the row it should update.
When the product has no manufacturer codes
Handmade goods, custom prints, vintage items and books printed before 1970 usually have no GTIN and no MPN. For these, Google’s answer is identifier_exists set to no, which says the codes do not exist, rather than leaving the gap unexplained.
Do not set identifier_exists to no for a product that does have a GTIN. Google says a product set that way when there is evidence a code exists will receive a warning.
Why getting this right pays off
Identifiers help Google recognise that your listing is the same product as others, and Google says the display of product ratings depends on accurate GTINs, MPNs and brand names. The guide on whose reviews show covers what that means for your stars, and the product feed guide shows where these attributes sit among the rest.
Questions
What is the difference between GTIN, MPN and SKU?
The GTIN is the manufacturer’s barcode number and the MPN is the manufacturer’s part number; both belong to the manufacturer. The SKU is the seller’s own stock code, which usually becomes the id in a Google feed.
Is MPN the same as SKU?
No. The MPN is the manufacturer’s part number, and it stays the same whoever sells the product. The SKU is a seller’s own stock code, so two shops selling the same item usually have different SKUs. They only match when the manufacturer sells its own products and uses its part number as its SKU.
Is SKU the same as GTIN?
No. A GTIN is the barcode number (UPC, EAN, JAN or ISBN) that the brand owner gets from GS1, and it is identical for every seller of that product. A SKU is your internal code. In a Google feed the GTIN goes in the gtin attribute and your SKU usually goes in id.
Can I make up a GTIN for my products?
No. Google says not to guess or make up a value. If you are the brand owner, get GTINs from GS1. If the product has no GTIN, such as a handmade item, set identifier_exists to no.
Is MPN required in Google Merchant Center?
Only when the product has no GTIN assigned by the manufacturer. Unless you are the manufacturer, Google says not to use an MPN you created.
Read next
Whose reviews show on your Google Shopping listing? Not always yours
Google compiles product stars from merchants, aggregators, review sites and users. Why a branded product’s rating is shared, and which stars are yours alone.
What is a product feed? The file behind every Shopping listing
A product feed lists every product as one row of attributes. What goes in it, what Google requires, and why channels read it instead of your product pages.
Why are my products not showing on Google Shopping? A diagnosis in order
Start with the product status in Merchant Center. What each status means, the issues that block products, and why an approved product still may not appear.