SKU and barcode sit next to each other on a Shopify product, and they are easy to confuse. This guide explains what a SKU is, how it differs from a barcode, why it matters for your store and the mistakes that cause stock errors.
What a SKU is
SKU stands for stock keeping unit. It is a code you create yourself to identify one sellable item, down to the variant. Shopify's help page describes SKUs as codes you can use internally to track your inventory and report on your sales, and it states that SKUs are different from barcodes and are used for different purposes.
| SKU | Barcode (GTIN) |
|---|---|
| Assigned by you | Assigned by the manufacturer |
| Used inside your store | Shared by every seller of that product |
| Any format you choose | A fixed number of digits |
A concrete example
You sell a cotton t-shirt in two colors and three sizes. That is six variants, so six SKUs. A readable pattern makes each one obvious at a glance.
- TEE-BLK-S: Black, small
- TEE-BLK-M: Black, medium
- TEE-WHT-L: White, large
The barcode on the same shirt, if the manufacturer printed one, is a string of digits that means nothing to a person reading it. Another retailer selling that shirt shares the barcode, but their SKU for it will be their own.
Why it matters for a store
Shopify says SKUs are not required, but you need a stable way to refer to each variant in order to count stock, read sales reports and place supplier orders.
- Inventory: Stock counts and reorder decisions are made per SKU
- Reporting: Sales can be compared variant by variant
- Fulfillment: Pickers can match a pick list to a shelf label
Common mistakes
Shopify's guidance is that SKUs in your admin should be unique, with no two variants sharing one. It also suggests keeping them short, using consistent abbreviations, and avoiding spaces and special characters.
- ❌ Giving two variants the same SKU
- ❌ Pasting the barcode into the SKU field, or the SKU into the barcode field
- ❌ Changing SKUs after orders and reports already use them
- ❌ Using characters that look alike, such as the letter O and a zero
- ✅ One pattern, applied the same way to every product
For barcodes and Google's identifier rules, see GTIN, MPN and brand for Google. Once your SKUs are clean, see how to calculate a reorder point.
Doing this at scale
StockSense forecasts per-SKU demand from your order history using velocity, trend, seasonality and lead-time-aware safety stock. It recommends a reorder point, quantity and date, ranks SKUs by revenue at risk, and drafts purchase orders grouped by supplier. See StockSense.