UPC, GS1 and Barcodes for Amazon
Barcodes confuse almost every new Amazon seller, and buying the wrong ones can get listings blocked. This guide explains UPCs, GS1, and FNSKUs in plain terms, and which you actually need to create a listing and ship to FBA.
You generally need a GS1-issued UPC to create a listing, and an FNSKU label on each unit for FBA. Cheap resold UPCs risk listing errors, so buy from GS1.
What's in this guide
What a UPC actually is
A UPC is the standard product barcode that identifies an item universally. On Amazon, you typically need one to create a new product listing, because it becomes the products global identifier in the catalog. It is the code the world uses to recognize your product, distinct from any Amazon-internal label. Getting this right at listing creation avoids errors that are painful to fix later.
Why GS1-issued codes matter
Amazon increasingly verifies that a UPC is genuinely issued by GS1, the official global standards body, and that the brand it is registered to matches your listing. Cheap bulk UPCs resold by third parties are registered to someone else, which can cause listing errors or removals. Buying your codes directly from GS1 costs more up front but avoids a category of problems that can freeze a listing. For a serious brand, it is the safe path.
UPC vs FNSKU
These serve different purposes and both matter. The UPC identifies the product and creates the listing. The FNSKU is Amazon internal barcode that ties a specific unit to your inventory in its fulfillment centers. Since Amazon stopped prepping inbound stock in 2026, your units must arrive already labeled with the FNSKU. So you use a UPC to list, and an FNSKU label on each physical unit to ship into FBA.
When you may be exempt
Not every situation requires you to buy a UPC. If you sell against an existing catalog listing, you may not need a new one, and some brand-registered sellers can apply for a GTIN exemption in certain cases. But for most new private-label products, a GS1 UPC is the starting point. Check your specific category rules rather than assuming, because requirements vary and getting it wrong stalls your launch.
How this fits your prep
In practice the flow is simple: buy GS1 UPCs, create your listings, then ensure every unit is labeled with its FNSKU before it reaches Amazon. That labeling is part of FBA prep, which now must happen before inventory arrives at a fulfillment center. Handling UPCs at listing time and FNSKUs at prep time, in the right order, keeps both your catalog and your inbound shipments clean.