Stock Keeping Unit — an internal identifier for a variant.
A SKU is an internal code assigned by the merchant to identify a specific variant across inventory, purchasing, accounting and analytics. Shopify does not require SKUs and does not enforce uniqueness, but nearly every downstream system does. Good SKUs are short, structured and human-readable — vendor code, category, attribute, size, color — and once assigned they should never change, because SKUs propagate to purchase orders, 3PL manifests, ad platform feeds and historical reports. Renaming a SKU without a mapping table is one of the fastest ways to break inventory reconciliation.
