What is a SKU?

A SKU (pronounced “skew”, short for Stock Keeping Unit) is a unique, human-readable alphanumeric code assigned internally by a merchant to identify a specific variant of a product for inventory management and order fulfillment.

Unlike universal barcodes (UPC/EAN), a SKU is internal to a specific merchant or business. Merchant A and Merchant B can sell the exact same Nike shoe, but each will create their own custom SKU format.

SKU Naming Conventions

Effective SKUs encode key product attributes directly into the code so warehouse staff and managers can recognize the item at a glance.

Example format: [CATEGORY]-[PRODUCT]-[COLOR]-[SIZE]

  • TSH-BLK-SM → T-Shirt, Black, Small
  • TSH-BLK-MD → T-Shirt, Black, Medium
  • TSH-WHT-LG → T-Shirt, White, Large
  • SHO-RUN-BLU-10 → Shoes, Running, Blue, Size 10

Why Do SKUs Exist?

  1. Unambiguous Fulfillment: Prevents warehouse pickers from shipping a Medium shirt when the customer ordered a Large.
  2. Multi-Location Inventory Tracking: Tracks stock counts for that exact item across warehouses, retail stores, and fulfillment centers.
  3. ERP & Accounting Integration: Syncs sales data between storefronts, ERPs, and accounting software.

Common Confusion

Developer Takeaway

SKU Uniqueness & Nullability: While merchants should ideally ensure SKUs are unique per variant, many ecommerce platforms (including Shopify) allow duplicate or empty SKUs. When building API integrations or inventory syncs, never use the SKU string as your primary database foreign key—always rely on the platform's immutable variant_id.