Guides · Barcode formats
FNSKU: The Amazon FBA Barcode Explained
If you sell through Amazon FBA, you stick a small label with a number starting with X00 on every product. That’s the FNSKU, and it determines whose inventory a unit is in the warehouse.
Key takeaways
- The FNSKU (Fulfillment Network Stock Keeping Unit) is an identifier Amazon assigns to products fulfilled by Amazon (FBA).
- It ties every unit in Amazon’s warehouse uniquely to you as the seller, so your inventory doesn’t get mixed up with the same product from other sellers.
- An FNSKU usually starts with X00 and is printed as a Code 128 barcode.
- Whether you need FNSKU labels depends on your barcode setting in Seller Central: Amazon barcode or manufacturer barcode.
FNSKU, ASIN, UPC and SKU: what’s what?
| Identifier | Who assigns it? | What for? |
|---|---|---|
| UPC/EAN / GTIN | GS1 (via the manufacturer) | Identifies the product worldwide, in retail and on Amazon |
| ASIN | Amazon | Identifies the product detail page in the Amazon catalog |
| SKU | You | Your internal item number in your seller account |
| FNSKU | Amazon | Identifies your units in the FBA warehouse |
If ten sellers sell the same item, it has one ASIN and one UPC, but each seller has its own FNSKU for its FBA inventory. That’s how Amazon knows whose stock a unit comes from when it ships.
When do you need FNSKU labels?
In Seller Central, you choose how your products are identified in the FBA warehouse:
- Amazon barcode: Every unit gets an FNSKU label that covers the manufacturer barcode. Your inventory stays separate from other sellers’. This is required for products without a valid GTIN and for many used items, among others.
- Manufacturer barcode: Amazon uses the existing UPC or EAN without an extra label. Amazon ended commingled storage of such inventory from different sellers in 2026; since then, going without your own label mainly applies to brand-registered products. Seller Central shows which option applies to your items.
The exact requirements change from time to time, so check the current labeling requirements in Seller Central before your first shipment.
What does an FNSKU label look like?
- A Code 128 barcode with the FNSKU
- The FNSKU in human-readable text below it (e.g. X00…)
- The product name, shortened if necessary
- The condition, e.g. “New”
You print the labels directly from Seller Central, usually on sheets with multiple labels. What matters is that the label lies flat, isn’t creased and completely covers the original barcode, so the wrong code doesn’t get scanned in the warehouse.
Check your FBA shipment before sending it
The most common mistake with FBA shipments: wrong or missing labels and quantities that don’t match the shipping plan. A quick check before you seal the boxes saves headaches:
- Lay out the labeled units from one box side by side, labels facing up.
- Photograph them with Scan2List: Inventory Scanner. The app reads all the FNSKU barcodes in the photo at once and adds up identical codes.
- Export the list as CSV and compare FNSKUs and quantities with the shipping plan from Seller Central, for example with XLOOKUP in Excel.
- If an FNSKU is missing, or a manufacturer barcode shows up that should be covered, fix it before the box goes to Amazon.
Tip: You can skip the spreadsheet reconciliation if you load the list into the Inventory mode of Scan2List first. Then the app compares while you take photos and shows you what is missing, where the quantity is off and what is not on the list. Check a delivery or shipment with the app ›
This is also how you find out whether a manufacturer barcode is still visible: it shows up as an extra UPC entry in the list.
Common mistakes with FNSKU labels
- Labels for different variants (color, size) mixed up
- Manufacturer barcode not completely covered
- Label stuck over an edge or curve so the code is distorted
- Wrong print format: the code is printed too small or blurry
Frequently asked questions
Where do I find my FNSKU?
In Seller Central, in the inventory overview of your FBA listings and when you create a shipping plan. You can also print the labels there.
Is the FNSKU the same as the ASIN?
No. The ASIN identifies the product in the Amazon catalog; the FNSKU identifies your specific units in the FBA warehouse. For listings that use the manufacturer barcode, the FNSKU can match the ASIN.
Can Amazon label my products for me?
Amazon scaled back or discontinued its FBA prep and labeling services in several marketplaces, including the US, in 2026. Check Seller Central to see whether the service is still offered in your marketplace. Alternatively, third-party prep centers can handle labeling for you.
Which app can I use to scan FNSKU codes?
FNSKU labels are Code 128 barcodes and can be read by any barcode scanner app that supports Code 128. Scan2List: Inventory Scanner captures several labels in one photo at once and exports them as a CSV.