- Short answer
- Use short, unique SKUs per variant, ideally 16 characters or fewer; Shopify's help has you enter them, except for Shopify Collective imports.
- Length
- 4–8 characters can be enough, depending on your catalog.
- Required?
- Not in general; cases needing them include Shopify Fulfillment Network, Shopify Collective and CSV imports with a custom fulfillment service.
- Adding later
- SKUs added after an order won't appear in historical reports.
What makes a good Shopify SKU format?
You can use any format (Flexport, as a Fulfillment Network 3PL, is stricter); Shopify offers guidelines:
- Characters: numbers, or numbers and letters, avoiding 0/1 versus O/I mix-ups.
- Separators: dashes and underscores, not special characters, symbols or spaces, which “can cause search problems”.
- Length: ideally no more than 16 characters; 4–8 can be enough, depending on your catalog.
- Unique: one per variant, so 3 sizes and 4 colors need 12 SKUs.
- Consistent: the same abbreviations everywhere, with combinations to spare as your catalog grows.
Shopify's examples: ####-###-### for apparel brand, style and size (4225-776-3234), and ###_###_## for pen wood, ink and point size (WAL_BLK_25).
ABC123 and abc123 as different SKUs, and Shopify's SKU help says to search with identical case and spacing, so check SKUs for symbols, spaces and mixed case before connecting an app.Does Shopify generate SKUs for you?
Shopify's SKU, CSV, Fulfillment Network and POS search pages, read October 31, 2026, describe no generator for the products you create; the one case we found where Shopify creates a SKU is Shopify Collective, for a retailer importing a supplier product that has none.
Enter each SKU in the Inventory section of every variant, not just the main product.
- Products
- Product
- Variant
Bulk changes go through the bulk editor or a product CSV (see bulk editing products).
Third-party SKU generator apps in the Shopify App Store offer to create codes, per their developers; settle your format first.
When are SKUs required in Shopify?
Shopify says “SKUs aren't required”, but some cases need them, and adding them later has a catch:
- Shopify Fulfillment Network: each variant needs a unique SKU before an outbound transfer, and Shopify says not to change a SKU after you submit it to your 3PL. With Flexport as that 3PL, SKU values “must not contain spaces or special characters”. Outside the network, a duplicate SKU triggers a warning.
- Shopify Collective: a SKU is required for every product sold through Shopify Collective.
- Custom fulfillment service: in a product CSV import, “The SKU column can't be blank”.
- Adding them later: SKUs added after an order won't appear in historical reports.
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