A Stock Keeping Unit (SKU) is a unique alphanumeric identifier assigned by a merchant to each distinct product variant in their inventory. Where a barcode (EAN or UPC) is a global standard shared across all retailers selling the same product, a SKU is merchant-defined and internal - specific to your business's inventory management system. On Shopify, every product variant (size, colour, material, bundle configuration) should have its own distinct SKU.
SKUs are the operational backbone of inventory management. They enable precise tracking of stock levels, reorder triggers, fulfilment accuracy (pick-and-pack teams identify items by SKU), supplier purchase orders, and sales reporting by variant. A Shopify store with 50 products and 5 variants each has 250 SKUs to manage - each one a trackable unit with its own stock count, cost, and sales history.
SKUs should not be confused with UPCs or EANs, which are globally standardised product identifiers used across all retailers. The SKU is yours alone. A well-structured SKU system uses a consistent naming convention that encodes meaningful information - product category, colour code, size - making it immediately readable to warehouse staff and inventory management tools without needing to look up a description. For brands using a 3PL for fulfilment, clean, consistent SKUs are essential: the 3PL's warehouse management system uses them to identify and pick the correct items for every order. SKU management also underpins demand forecasting - knowing which variants sell fastest, which are overstocked, and which need to be reordered connects directly to fulfilment efficiency and working capital management.
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