ASIN vs SKU: What Each Amazon Code Means and When to Use It

ASIN vs SKU: the core difference

Amazon’s seller guide defines the ASIN as the Amazon Standard Identification Number, a 10-character alphanumeric identifier assigned to products in Amazon’s catalog. It appears on the product detail page and helps Amazon organize and search the catalog.

A SKU, or stock keeping unit, is a code a business uses to track its inventory. In Seller Central, a seller SKU identifies your offer and ties it to your own inventory records.

You can enter your own SKU or let Amazon generate one. A consistent naming pattern helps your team match offers to the right products when preparing orders or replenishing stock.

How the ASIN and SKU work together

When you list a product, you attach your SKU to the ASIN. That pairing is your offer. Amazon recommends preserving existing SKUs unless the product is deleted, since the SKU links the offer to your own inventory records while the ASIN stays the catalog anchor.

Two sellers may offer the same branded phone case under one ASIN. One seller might use CASE-BLK-IP15 as its SKU and the other might use PC0042. The product’s catalog identifier stays the same.

Is a SKU unique?

Each offer in your seller inventory needs its own SKU. Keep the SKU stable once the offer is created, and check the SKU column before uploading an inventory file. An update with an existing SKU can modify the associated offer.

What does a good SKU look like?

Give each sellable variation its own SKU. Amazon’s SKU guide uses attributes such as product type, color and size to make codes easier to recognize.

A simple pattern that works for most small sellers:

1. Start with a product-type code (MUG, TEE).
2. Add the variation (BLK, L, 12OZ).
3. Add a batch or supplier code if you reorder from several factories.
4. Keep it short, readable and free of spaces and look-alike characters such as O and 0.

Decide the pattern once, before your first purchase order. Renaming later is painful because the SKU cannot simply be edited.

UPC vs ASIN

A UPC-A barcode encodes a 12-digit GTIN used to identify a product across retailers. An ASIN identifies that product within Amazon’s catalog. Keep both values in your inventory records if the product has them. See Amazon’s guide to product identifiers.

When listing an existing product, use its product ID to find the matching ASIN and confirm the brand, model and pack size before adding your offer. A different pack size or variation may have its own product identifier.

FNSKU vs ASIN vs UPC

The FNSKU, or Fulfillment Network Stock Keeping Unit, identifies an offer in Amazon’s fulfillment network. When an offer requires an Amazon barcode, its unit label carries the FNSKU.

Keep a record that maps each seller SKU to its ASIN, GTIN where applicable, and the FNSKU shown on the offer’s Amazon barcode label.

FNSKU label requirements

For U.S. FBA shipments sent on or after March 31, 2026, eligible brand owners with the Brand Representative selling role in Amazon Brand Registry can use a qualifying manufacturer barcode. Resellers must use Amazon barcodes even when the product has a manufacturer barcode. Products without a manufacturer barcode require an Amazon barcode. Check Amazon’s FBA barcode requirements and the barcode assigned to your offer.

When Amazon requires its barcode, print the label for the exact offer in Seller Central. Follow Amazon’s labeling instructions for placement and cover competing scannable product barcodes as directed.

• Scannable, showing the FNSKU, product name and condition.
• Black ink on a non-reflective adhesive label.
• Use a label size supported by Seller Central and verify that the barcode scans.
• Placed flat on a smooth exterior surface, away from corners, edges and curves.

When using Amazon barcodes, confirm the label on each sellable unit. The outer shipping box carries its own shipment labels. See our FBA packaging guide and our FBA shipment creation guide.

Where SKU choices show up in your shipment

Check the preparation and labeling instructions in Seller Central for each SKU in the shipment. Share a file with the SKU, product variation, unit barcode, units per carton and any set or prep instructions with your supplier or prep team.

For sellers importing from overseas, this means the codes should be final before production ends. Labels applied at the factory, or at a prep step on the way, only help if the SKU, FNSKU and shipment plan agree. A mislabeled carton can slow check-in at the fulfillment center, which hurts most when you are racing a seasonal deadline. Our Black Friday inventory timeline shows how far ahead to lock this in.

FAQ

Is a UPC the same as an ASIN?

A UPC identifies a product across retailers. An ASIN identifies a product in Amazon’s catalog. When adding an offer, Seller Central can use the product ID to find an existing listing. New catalog entries may require a GTIN or an approved exemption.

Can you give an example of a SKU?

For a blue medium T-shirt, you could use TEE-BLU-M-01. The parts identify the product type, color, size and series.

Is a SKU code unique?

A seller SKU is unique to an offer in your seller inventory. Different sellers can use their own SKUs for offers on the same ASIN.

What is the difference between an FNSKU and an ASIN?

An ASIN identifies the product in the catalog. An FNSKU identifies an offer in Amazon’s fulfillment network and appears on its Amazon barcode label when that label is required.

Do I always need an FNSKU label?

For U.S. FBA, eligible brand owners can use qualifying manufacturer barcodes. Resellers and products without a manufacturer barcode require an Amazon barcode. Check Amazon’s requirements for your offer.