Product identifiers (GTIN, EAN, SKU) explained: why they decide whether your listings go live
A GTIN identifies a product in the world; a SKU identifies it in your own system. Confusing the two, or getting either wrong, is one of the most common reasons listings are held back. Here is how to keep them clean.
Most sellers think of a listing as a title, photos and a price. For a marketplace, the first thing that matters is often something less visible: the identifier. It tells the platform which product you are offering, and whether that product already exists in its catalogue.
GTIN, EAN, UPC and SKU: two different jobs
GTIN is the general name for the barcode numbers assigned to a product by its manufacturer or brand owner. EAN and UPC are formats of GTIN used in different regions. These numbers are shared by everyone who sells that product. A SKU is the opposite: a code you invent for your own stock-keeping, which means nothing outside your business. One identifies the product for the world, the other identifies your item inside your system. Both are needed, and neither replaces the other.
Why marketplaces match offers on identifiers
Many marketplaces build one product page and attach several offers to it. To do that, they need a reliable way to know that two sellers are offering the same thing, and a title is far too loose for that. The GTIN is the key. If it is missing, the platform may ask for more information or refuse the listing. If it is wrong, your offer may be attached to the wrong product. Each platform has its own requirements, so check them for every channel you use.
Common errors and how to avoid them
- Missing identifiers: a blank field is the simplest cause of a held-back listing. Track which products have no GTIN, and handle them on purpose rather than by accident.
- Duplicates: the same GTIN on two different products, or the same SKU used twice, creates stock and order mix-ups. Check for uniqueness before importing.
- Wrong check digit: the last digit of a GTIN is calculated from the others. A typo, a lost leading zero or a number mangled by a spreadsheet makes it invalid. Validate the digit automatically.
- Variations: each size or colour is a distinct item and normally needs its own identifier, not the one from the parent product.
- Different codes per channel: keep one identifier per product everywhere, so stock, orders and returns can be traced back to the same item.
Future Point stores the GTIN and your SKU together in one product catalogue, checks the format before anything is published, and reuses the same identifiers on every channel. The live demo on this site shows how a product record carries them.