SKU (Stock Keeping Unit)
A unique code assigned to one specific version of a product so a business can track it in inventory.
What is SKU (Stock Keeping Unit)?
A SKU (Stock Keeping Unit) is a unique code (usually a short string of letters and numbers) that a business assigns to one specific, sellable version of a product so it can track inventory, sales, and stock levels for that exact item. A t-shirt that comes in three sizes and two colors typically gets six different SKUs, one per size-color combination, even though it's "one product" from a shopper's perspective.
Why it matters
A SKU is an internal identifier: each company invents its own SKU scheme, and no external body registers or standardizes them, which is why the same physical product can carry a different SKU at every retailer that stocks it. That's the key contrast with the GTIN (Global Trade Item Number), the barcode-encoded identifier issued under GS1's global standard and made up of a company prefix, item reference, and check digit, which is assigned once per product and stays constant across every retailer selling it. Merchants commonly map their internal SKU to a product's GTIN/UPC in their product data so that internal inventory systems and external channels, like marketplaces and ad platforms, can be reconciled against the same underlying item.