Everything you need to know about FNSKU labels for Amazon FBA. What FNSKU means, how to generate your FNSKU barcode, printing specs, application rules, and common mistakes to avoid.
FNSKU stands for Fulfillment Network Stock Keeping Unit. It's Amazon's internal barcode system that links a specific product to a specific seller account within Amazon's fulfillment network.
Unlike a UPC (Universal Product Code) or EAN (European Article Number) — which are universal identifiers anyone can use — an FNSKU is unique to your seller-ASIN combination. No two sellers have the same FNSKU for the same product.
This uniqueness is critical: it allows Amazon to track exactly whose inventory is in each fulfillment center, route returns correctly to the original seller, and prevent co-mingling of inventory from different sellers.
Generating an FNSKU is straightforward once you have an Amazon seller account:
1. Log in to Amazon Seller Central
2. Navigate to Inventory → Manage Inventory
3. Click on the product you want to label
4. Click 'Print item labels' from the dropdown menu
5. Select the label size (typically 1" × 2" or 2" × 1")
6. Download the PDF and print
Alternatively, when creating an FBA shipment:
1. Start a new shipment in Manage FBA Inventory
2. Select your products
3. During shipment creation, Amazon gives you the option to print FNSKU labels for all units in the shipment
Note: the FNSKU barcode changes only if you create a new ASIN or your existing ASIN's condition changes. The same product on the same ASIN will always have the same FNSKU.
Amazon uses several barcode types that sellers often confuse:
FNSKU: The seller-specific product label. Required if you're not using manufacturer barcodes.
ASIN: Amazon Standard Identification Number — a 10-character alphanumeric code that identifies the product listing. Not a scannable barcode by itself.
UPC/EAN: Manufacturer barcode. Can be used for FBA if you're enrolled in Amazon's Transparency program or have opted for commingled inventory.
Amazon Transparency Code: A serialized, unit-level anti-counterfeiting code. Required for some brand-enrolled products.
X00 codes: Variation of ASIN for bundled products.
For most FBA sellers: FNSKU is what you print and apply to every unit. Everything else is secondary.
Recommended printers:
• Zebra ZP450, ZD420, GK420d (thermal)
• Rollo Label Printer (thermal)
• DYMO LabelWriter 450 (thermal)
• Standard laser printer with label sheets (acceptable but lower volume)
Label stock:
• 1" × 2" thermal labels (most common for FBA units)
• 2" × 1.25" for slightly larger products
• 4" × 6" for box labels
Print settings:
• Resolution: 300 DPI minimum for reliable scanning
• No scaling — print at 100% actual size
• Test scan before printing a full batch
• Avoid inkjet — it can smear when wet
At QuickShipment, we use commercial-grade thermal printers and verify every label with a barcode scanner before application.
Applying FNSKU labels correctly is as important as printing them correctly:
Step 1: Identify the existing barcode on the product packaging. The FNSKU must cover it or be positioned so only the FNSKU is scannable.
Step 2: Find the flattest, most accessible surface on the product or its packaging. Avoid curved surfaces, seams, or transparent windows.
Step 3: Apply the label firmly and smoothly. No air bubbles, wrinkles, or folds. If the label is on a poly bag, ensure it won't shift position.
Step 4: Scan the barcode with a handheld scanner. Confirm it reads the correct FNSKU. If it doesn't scan cleanly, replace the label.
Step 5: Verify the human-readable text below the barcode matches the FNSKU on your shipment plan.
Step 6: If the product is poly-bagged, apply the FNSKU label to the outside of the bag after sealing.
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