Amazon FBA Barcode Requirements — FNSKU, UPC, and What You Actually Need
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Amazon FBA has specific barcode requirements that trip up new sellers constantly. The confusion usually comes from two different barcode systems operating at the same time: the retail barcode on your product (UPC or EAN) and Amazon's own internal barcode (FNSKU) that goes on the FBA label.
This guide explains exactly what each barcode is, when you need each one, and how to generate or obtain them correctly.
The Two Barcode Systems Amazon FBA Uses
There are two completely separate barcodes involved in selling on Amazon FBA:
| Barcode | What It Is | Where It Goes | Who Creates It |
|---|---|---|---|
| GTIN (UPC/EAN) | Retail product identifier, GS1-registered | On the product itself (manufacturer label) | You, from GS1 |
| FNSKU | Amazon's internal fulfillment code | On the FBA shipping label (covering or replacing the product barcode) | Amazon, from Seller Central |
Most new sellers need both. The UPC/EAN to create and match your Amazon listing. The FNSKU label to physically label the product before sending to FBA warehouses.
What Is an FNSKU Barcode?
FNSKU stands for Fulfillment Network SKU. It is a CODE128 barcode that Amazon assigns to each seller-ASIN combination in their system. It looks like: X001234567 — an X followed by 9 digits.
The FNSKU does two critical things in Amazon's warehouse:
- Identifies your specific unit: Two different sellers selling the same product have different FNSKUs. This ensures Amazon picks your inventory, not a commingled competitor's.
- Prevents commingling issues: Without FNSKU labels, Amazon may use "stickerless commingling" — pooling your inventory with other sellers of the same ASIN. This can expose you to negative reviews from counterfeit or lower-quality products shipped in your name.
You do not generate FNSKU barcodes yourself. Amazon generates the FNSKU value and you print the label from Seller Central. The label is a CODE128 barcode — this free generator can recreate the barcode image if you know your FNSKU value, but the authoritative source is always Seller Central.
Sell Custom Apparel — We Handle Printing & Free ShippingDo You Need a UPC/EAN to Sell on Amazon?
For most product categories, yes. Amazon requires a GTIN (UPC, EAN, ISBN, or ASIN) to create a new product listing.
| Situation | UPC/EAN Required? |
|---|---|
| Creating a new product listing (most categories) | Yes — must match GS1 registry |
| Selling under an existing ASIN (matching a listing) | Yes — GTIN needed to match |
| GTIN Exemption (approved brand, handmade, etc.) | No — Amazon grants exemption for eligible sellers |
| Amazon private label brands | No — you get an Amazon-issued ASIN directly |
GTIN Exemption: If you manufacture your own products, sell under a registered brand, or sell in certain categories (handmade, certain collectibles), you can apply for a GTIN exemption in Brand Registry or through a Seller Central request. Approved sellers can create listings without a GS1 UPC.
Amazon FBA Label Specifications
When printing FNSKU labels to apply to products before sending to FBA:
- Recommended label size: 1" x 2.625" (Avery 5160 compatible) or 2" x 1"
- Barcode format: CODE128 (generated automatically by Seller Central)
- Minimum barcode size: Must be scannable from 6-8 inches with a standard barcode gun
- Print quality: High contrast black on white — no gray, no colored labels
- Placement: Must cover any existing manufacturer barcode on the product — Amazon's warehouse scanners should hit your FNSKU first
- Font: FNSKU code printed in human-readable text below the bars (included automatically)
Print FNSKU labels from Seller Central: Inventory > Manage Inventory > select items > Print item labels. Amazon generates the correct CODE128 barcode at the right size.
Generating UPC or EAN Barcodes for New Amazon Product Listings
If you are creating a new product that will be sold on Amazon and in other retail channels, you need a GS1-registered UPC or EAN:
- Register a company prefix with GS1 US (gs1us.org) — from ~$50/yr for a single product
- Assign a product number to each item variant
- Generate the barcode image using this tool (select UPC or EAN13, enter your number)
- Apply the barcode to your product packaging
- Enter the UPC/EAN when creating your Amazon listing
Amazon now cross-checks your entered UPC against the GS1 registry to verify you own the prefix. Resold UPC barcodes from third-party sellers will fail this check. Always register directly with GS1.
For the full guide to generating retail UPC barcodes, see the UPC barcode generator guide.
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Open Free Barcode GeneratorFrequently Asked Questions
Does Amazon accept EAN-13 barcodes for US listings?
Yes. Amazon accepts UPC-A (12 digits), EAN-13 (13 digits), ISBN, and GTIN-14. For US-based products, UPC-A is traditional, but EAN-13 works fine. Amazon's system handles both.
Can I use the same UPC barcode for Amazon and other retailers?
Yes — a GS1-registered UPC is a universal product identifier. The same UPC you use to list on Amazon can be used at Target, Walmart, Costco, or any other retailer. That is the entire point of the GS1 system.
What happens if I send products to FBA without FNSKU labels?
Products without FNSKU labels will be either commingled with other sellers' inventory (if you have stickerless commingling enabled) or flagged as non-compliant. Amazon may apply labels themselves for a per-unit fee (~$0.20-0.55/unit), or the shipment may be refused. Always label before sending.
Chris has been in digital marketing for twelve years as an independent consultant. He covers SEO tools, meta-tag generators, and content optimization — writing for marketers who need practical tools, not theory.
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