What is a stock keeping unit (SKU)?

A SKU (Stock Keeping Unit) is a unique, internal alphanumeric code used by retailers and fulfillment providers to identify and track specific products within an inventory system. Unlike a UPC (Universal Product Code), which is standardized for external use across all retailers, a SKU is merchant-specific, allowing a business to customize its inventory architecture based on attributes like size, color, material, and warehouse location.