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What Is an FNSKU? Amazon's FBA Unit Label Explained
FNSKU is the X00-prefixed barcode Amazon assigns to every FBA SKU. Here is what it means, why every unit needs one, and how to print them.
FNSKU stands for Fulfillment Network Stock Keeping Unit. It is a unique Code 128 barcode (always starting with 'X00') that Amazon assigns to each of your FBA SKUs. Every unit you ship to an Amazon fulfillment center must carry an FNSKU label so Amazon can trace inventory back to your seller account, distinguishing your units from other sellers' identical products.
FNSKU is internal to Amazon's FBA network — it doesn't appear on retail packaging at the store. The FNSKU lives on a removable sticker applied over any existing UPC/EAN barcode, ensuring Amazon's warehouse scanners read YOUR identifier, not the manufacturer's.
How an FNSKU is structured
FNSKU is 10 alphanumeric characters: always 'X00' (the Amazon prefix) followed by 7 random letters and digits. Example: X00ABC1234. The barcode itself is a standard Code 128 rendering of that string. Amazon assigns one FNSKU per SKU (not per unit) — 1,000 units of the same SKU all share the same FNSKU.
FNSKU vs SKU vs ASIN: the three codes
SKU is your INTERNAL product code — you choose the format and naming, it's private to your business. ASIN is Amazon's CATALOG code — identifies the product listing customers see (shared across all sellers of the same product). FNSKU is Amazon's FULFILLMENT code — identifies which physical unit belongs to which seller inside FBA warehouses. Each SKU has exactly one FNSKU and one ASIN (though multiple sellers can list under the same ASIN with different FNSKUs).
How to get an FNSKU label
In Seller Central: Inventory → Manage Inventory → find your FBA SKU → action menu → 'Print item labels'. Choose label size (1×2 inch is Amazon's standard) and quantity. Download PDF. Print on white removable labels in black ink. Apply each label flat over any existing manufacturer barcode on the unit. As of January 2026, Amazon no longer applies FNSKU labels for sellers — you MUST apply them before shipping to FBA.
FNSKU label requirements (Amazon spec)
Size: 1×2 inches (25×51 mm). Color: black ink on white non-reflective label. Adhesive: removable (so customers don't see them). Placement: flat, fully covering any existing UPC/EAN barcode on the product packaging. Quality: must scan cleanly — low-contrast prints or wrinkled labels get rejected at FC receiving. Use a thermal label printer (Rollo, Zebra) or 30-up Avery 5160 sheets through a laser printer.
FAQ
What is an FNSKU label?
FNSKU stands for Fulfillment Network Stock Keeping Unit. It's a unique Code 128 barcode (starting with 'X00') that Amazon assigns to each of your FBA SKUs. Every unit shipped to Amazon FBA needs an FNSKU label so Amazon can trace it back to your seller account.
Are SKU and FNSKU the same?
No. SKU is your internal product code — you set the format, it's private to your business. FNSKU is the Amazon-generated code Amazon uses inside its fulfillment centers — format is fixed (X00 prefix + 7 alphanumeric chars). Each SKU has exactly one FNSKU.
Where can I find FNSKU labels?
In Amazon Seller Central: Inventory → Manage Inventory → find your SKU → action dropdown → 'Print item labels'. Choose label size and quantity, download as PDF, print on 1×2 inch removable labels. The PDF contains your FNSKU as a Code 128 barcode plus the human-readable text below.
Are ASIN and FNSKU the same?
No. ASIN identifies the product listing in Amazon's catalog (visible to shoppers). FNSKU identifies which physical unit belongs to which seller inside Amazon's warehouses (internal only). One ASIN can have multiple FNSKUs from different sellers offering the same product.
How do I get an FNSKU label?
Sign in to Seller Central → Inventory → Manage Inventory → find your FBA SKU → action menu → 'Print item labels' → choose quantity and format → download PDF. As of Jan 2026, Amazon no longer applies FNSKU labels for sellers — apply them yourself before shipping.
What size should an FNSKU label be?
Amazon spec: 1×2 inches (25×51 mm) removable label, printed in black ink on a white non-reflective surface. Apply flat over any existing manufacturer barcode (UPC, EAN) to prevent the FC scanner from reading the wrong code.
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