GTIN = Global Trade Item Number

GTINs are global codes that allow organizations and authorities to identify products. GTIN codes include UPCs (Universal Product Code) and EANs (European Article Number) that manufacturers or sellers are obligated by law to put on their products.

GTINs can be purchased from authorized companies such as GS1.

UPC = Universal Product Code

UPCs are used on products that sell in brick and mortar stores and online around the world. Pick up just about any product in your home, and you'll probably see a UPC on it or its package.

All around the world, there no two UPCs that is identical. Every UPC has 12 digits and is unique to just one product, so it is easy to identify that product when the barcode is scanned or looked up.

The law requires adding a unique UPC barcode for each product that you sell. But, if you have 500 units of the same product, you don't need 500 different UPCs - you only need one, and that same one goes on each of the 500 units.

EAN = European Article Number

European Article numbers, or EAN barcodes, are similar to UPCs, except they have 13 digits instead of 12. A digit is added at the beginning of the EAN code signifying the country of issue or retail type. Just like UPCs, every EAN barcode is unique to one product.

ISBN = International Standard Book Number

Amazingly, when Amazon originally opened for business years ago, the site only sold books! So one of the first barcodes you would have found on Amazon at that time were ISBNs. A unique ISBN will be found in every published book worldwide.

Publishers obtain ISBNs for books they publish, and if you self-publish on Amazon, you will automatically be issued an ISBN for each book you publish on the platform.

ASIN = Amazon Standard Identification Number

An ASIN is automatically assigned to an Amazon listing when it is created. Hence many people refer to listings and ASINs or vice versa. ASINs are 10 alphanumeric digits long and always start with "B0". ASINs are Amazon's way of identifying a listing/product on their site.

FNSKU = Fulfillment Network Stock Keeping Unit

Amazon assigns an FNSKU to listings that are Fulfilled by Amazon (FBA). When sending in inventory to Amazon, every unit should have its FNSKU barcode on it. This is how Amazon knows that the incoming units are yours.

FNSKUs are also 10 alphanumeric digits long and always start with "X0". If you are about to send inventory to Amazon and your FNSKU labels do not start with "X0" something is wrong, and you need to fix it ASAP to the correct barcode.

If you are an FBA seller, you will need to give the product's FNSKU barcode (starting with "X0") to your supplier so they can label each unit, or you can have it incorporated in your product's packaging design.

SKU = Stock Keeping Unit

SKU is the one identification number that you, as the seller, can choose. When creating a new listing (ASIN), you will be able to type in whatever you like in the SKU field. Type in a descriptive product name that will help you identify the product / that particular variation every time you see the SKU instead of a numeric code that'll be difficult to remember and identify when you have many products.

For example, if you set up 3 color variations of a baseball cap, you'll have to set a unique SKU for each variation. The SKU could include the color of a variation (something like {Product name} - {Color} - {Fulfillment type}). Only you will see the SKU, so don't be worried that Amazon shoppers may see the name.