Brand ownership without owning the factory · Three identifiers, three jobs
FNSKU vs ASIN vs UPC
ASIN identifies the catalog item, FNSKU labels the seller's inventory at Amazon, and UPC/EAN is the product's GTIN.
Key facts
| ASIN | Amazon's catalog identifier for a product |
|---|---|
| FNSKU | Amazon's fulfillment label that ties a unit to a seller |
| UPC/EAN | The product's GTIN, usually from GS1 |
| Label placement | Must cover the original barcode and be scannable |
| Commingling | Without FNSKU labeling, inventory may be commingled with other sellers |
| Catalog match | A wrong GTIN can attach the listing to the wrong product |
| Official source | Amazon Seller Central labeling and catalog guidance |
The FNSKU is about ownership
The ASIN tells Amazon which product it is. The FNSKU tells Amazon which seller's unit it is. If you send inventory without the right FNSKU label, your units can be commingled or received incorrectly.
Check the label format and placement before the cartons leave the factory. A label that covers the product's original barcode is usually required.
A GTIN mismatch creates catalog problems
If the GTIN on the packaging does not match the ASIN, the listing can attach to the wrong product or fail validation. Fix the catalog data before shipping, not after the units are in the fulfillment center.
Keep a mapping table: product, variant, GTIN, ASIN, FNSKU and packaging version.
Frequently asked questions
Can I use the same FNSKU for different products?
No. Each seller-product combination needs the correct FNSKU. Reusing one can mislabel inventory.
Is an ASIN a barcode?
No. An ASIN is Amazon's catalog identifier. A UPC or EAN is the barcode that encodes the GTIN.
Ask a compliance question
Free first answer by email. Tell us the destination, the product and the channel — we will point you to the rule and the official source. No obligation, no sales sequence.