UPCBay

What Is a SKU?

SKU stands for Stock Keeping Unit — an internal code a business assigns to a product to track it in inventory. Unlike a UPC, which is standardized and universal, a SKU is whatever you want it to be. You make it up. It only means something inside your own system.

Real example

A clothing brand might assign SKU 'SHIRT-BLU-L' to a blue shirt in size Large. Their competitor sells the exact same shirt and calls it 'ITEM-472'. Both SKUs refer to products that might share the same universal UPC. The SKUs are private; the UPC is public.

How a SKU is used in e-commerce

  • Shopify, WooCommerce, and most e-commerce platforms have a SKU field for each product variant.
  • Amazon Seller Central lets you assign a 'Seller SKU' alongside the GTIN — useful for matching Amazon inventory to your internal system.
  • 3PL (third-party logistics) warehouses often use your SKUs to organize pick-and-pack operations.
  • Purchase orders and invoices between you and your supplier typically reference SKUs, not UPCs.

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Common questions

Related terms

UPC codeGTINASINUPC vs SKU