Stock Keeping Unit (SKU)
A SKU (pronounced “skew”) stands for Stock Keeping Unit. It is a unique identifier assigned to a specific product or product variant in an inventory system. Every distinct item a seller carries gets its own SKU so that it can be tracked, ordered, and managed individually.
For example, a t-shirt that comes in three colors and two sizes has six different variants. Each variant gets its own SKU, because the blue medium and the red large are different items, even if they come from the same product listing.
SKUs in Detail
A SKU is typically an alphanumeric code created by the seller. Unlike a barcode (which is a standardized industry identifier), a SKU is internal. The seller defines the format and assigns it. For example: TSHIRT-BLU-M could be the SKU for a blue medium t-shirt.
SKUs serve several practical functions:
- Inventory tracking. SKUs allow sellers to know exactly how many units of each specific variant are in stock at any time, across one or multiple locations.
- Order management. When an order is placed, the SKU tells the fulfillment system which exact item to pick and ship, reducing errors.
- Performance analysis. Tracking sales, refunds, and returns by SKU reveals which specific variants sell well and which underperform.
- Supplier communication. SKUs are used when reordering from suppliers to ensure the right items are restocked, rather than describing products in general terms.
- Platform integration. Most eCommerce platforms, including Shopify, Amazon, and eBay, use SKUs to sync inventory and identify products across systems.
This makes SKUs the backbone of organized inventory management. A seller without a SKU system can easily lose track of what’s in stock, oversell out-of-stock variants, and struggle to identify which products are profitable.
SKU vs. Barcode vs. UPC
These three terms are related but distinct.
- A SKU is an internal code created by the seller. It can be any format the seller chooses and is used within the seller’s own systems.
- A barcode is a machine-readable visual representation of a number. It’s the striped image scanned at a checkout or warehouse scanner.
- A UPC (Universal Product Code) is a standardized 12-digit number assigned by a recognized authority (like GS1). UPCs are required on many marketplaces, including Amazon and Walmart. They are globally consistent, meaning the same product has the same UPC regardless of who sells it.
A seller might use a SKU internally to track their variants while also assigning the manufacturer’s UPC to the same product for marketplace listings.
Why Are SKUs Important for eCommerce Sellers?
SKUs matter because, as a store grows, managing inventory without them becomes unmanageable. A dropshipping store with 50 products across multiple variants needs a way to identify each item precisely, especially when tracking refund rates, reorder points, and supplier communications.
Most eCommerce platforms assign SKUs automatically if a seller doesn’t create their own, but using a consistent, logical naming system from the start makes inventory management, reporting, and supplier communication significantly more efficient as the catalog grows.
Frequently Asked Questions
What does SKU mean in eCommerce?
SKU means Stock Keeping Unit in eCommerce. It is a unique code assigned to a specific product or variant so that it can be individually tracked in an inventory system. Every distinct item, including different sizes, colors, or configurations of the same base product, gets its own SKU.
Do I need SKUs for my Shopify store?
Yes, using SKUs for your Shopify store is strongly recommended, especially if you carry products with multiple variants. Shopify allows you to assign custom SKUs to each variant in your product editor. Without them, tracking inventory levels, identifying which variants need restocking, and analyzing product performance becomes significantly harder as your catalog grows.
What is the difference between a SKU and a UPC?
A SKU differs from a UPC in that a SKU is an internal identifier created by the seller for their own inventory system, while a UPC is a standardized, globally recognized product code assigned through a licensing authority like GS1. SKUs are used for internal management; UPCs are required for selling on many marketplaces and are the same for a given product regardless of who sells it.
