One wrong barcode choice means rejected inventory and manual processing fees. This guide cuts through the confusion — you'll know exactly which barcode to use within 2 minutes.
Fulfilment Network Stock Keeping Unit. An Amazon-generated Code-128 barcode that links a specific product to your seller account. Required for most FBA items.
Example format:
X00ABC123D
Universal Product Code. 12-digit global product identifier used primarily in North America. Required on products before Amazon assigns an FNSKU. Cannot replace the FNSKU for FBA labelling.
Example format:
012345678905
European Article Number. 13-digit international product identifier — the UK/EU equivalent of UPC. Used to create Amazon product listings, then must be covered by the FNSKU for FBA items.
Example format:
5901234123457
| Feature | FNSKU | UPC-A | EAN-13 |
|---|---|---|---|
| Scope | Amazon-only | North America | International |
| Digit count | 10 chars (Code-128) | 12 digits | 13 digits |
| Required for FBA item label? | ✓ Yes | ✗ No (must be covered) | ✗ No (must be covered) |
| Required for Amazon listing? | ✗ No | ✓ Yes (US/CA) | ✓ Yes (UK/EU) |
| Cost | Free | Paid (via GS1) | Paid (via GS1) |
| Generated by | Amazon Seller Central | GS1 organisation | GS1 organisation |
The relationship between FNSKU, UPC, and EAN confuses many sellers because they're used at different stages of the FBA process. Here's a clear breakdown of when each one matters and why you can't substitute one for another.
To create a new product listing on Amazon, you need a UPC (for the US/Canada marketplace) or EAN-13 (for UK/EU). Amazon uses these to match your product to their catalogue. This is where you spend money on GS1 barcodes — or use the GTIN exemption if you qualify.
Once your listing exists, Amazon assigns an ASIN (Amazon Standard ID) and an FNSKU to each product variation in your account. The FNSKU is what you actually put on the physical item.
When you send inventory to an Amazon fulfilment centre, each item needs a barcode that Amazon can scan when they receive it. This is the FNSKU — not the UPC or EAN. The FNSKU tells Amazon exactly who owns this inventory (your account), which listing it belongs to, and which warehouse location to route it to.
The original UPC/EAN on the packaging must either be covered by the FNSKU label or not visible at all. If both are visible, the scanner may read the wrong one.
Source: Amazon Seller Central — FBA product barcode requirements. Amazon requires FNSKU labels on all FBA inventory unless the seller has an approved manufacturer barcode exemption.
Some brand-registered sellers are granted a "barcode exemption" that allows them to use the manufacturer UPC/EAN instead of applying an FNSKU label. This only applies if Amazon has approved it for your account. Without the exemption, you must always use the FNSKU. When in doubt: use the FNSKU. It's always the safe choice.
No — unless you have been explicitly granted a manufacturer barcode exemption by Amazon. For the vast majority of FBA sellers, every item must have its FNSKU applied before sending to the fulfilment centre. The EAN/UPC on the original packaging must be covered.
Log in to Seller Central → Manage Inventory → find your product → click "Print item labels." The FNSKU is displayed on the label and also visible in the product detail within Seller Central. It always starts with X00 and is 10 characters long.
Yes. Each ASIN variation gets its own FNSKU. A red T-shirt in size Small has a different FNSKU from the same shirt in Medium or Blue. This is how Amazon tracks mixed-variation inventory at the unit level in their fulfilment centres.
Last updated June 2026 · freebarcodetools FBA team · Corrections? Let us know
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