The SKU is the identifier your business uses to track inventory, sales and logistics. If you sell t-shirts, each combination of model-size-color is a distinct SKU: TEE-BASIC-L-BLUE and TEE-BASIC-L-RED are two SKUs.
Unlike barcodes (which are global and unique per physical product), SKUs are internal. Two stores can sell the same product with completely different SKUs. Your competitor might call it SHIRT-001-BLUE-L while you use TOP-BL-L-001.
SKUs originated in physical retail to streamline inventory and replenishment. Today they're critical in e-commerce: they integrate your online store with ERP, fulfillment systems and marketplaces. Amazon, eBay and Shopify require each variant to have its unique SKU.
There's no official standard, but best practices recommend readable, scalable and unambiguous SKUs:
- Alphanumeric: combine letters and numbers. Avoid special characters that break legacy systems (
@#$%). - Segmented: use hyphens or positional structure to separate attributes.
CAT-SUBCATEGORY-ATTRIBUTE-SEQUENTIAL. - Short but descriptive: between 6 and 15 characters. Too short loses context, too long is error-prone.
- No spaces: spaces cause problems in URLs and databases. Use hyphens or CamelCase.
Real Zara example: 2335/420/800 (collection/model/color). Amazon example: B08N5WRWNW (ASIN, opaque but globally unique). Warehouse example: WHE-SHE-MET-BLK-42 (category-type-material-color-size).
Avoid starting SKUs with zeros: Excel and some systems interpret them as numbers and drop them. Prefer A001 over 0001.
E-commerce: each listed variant (product + selectable options) must have its SKU. If you sell sneakers in 10 sizes, that's 10 SKUs. Shopify, WooCommerce and similar platforms have dedicated fields.
Omnichannel inventory: SKUs sync stock across physical store, online and marketplaces. When someone buys on Amazon, your system deducts from the same inventory as your Brooklyn store.
Logistics: warehouses and 3PLs use SKUs for picking and packing. A well-designed code lets operators identify products without photos: BOK-FICT-KING-001 = book, fiction, Stephen King, first edition.
Analytics: sales reports by SKU reveal which products, colors or sizes move fastest. This informs future purchasing and pricing decisions.
Tools: ERPs like Odoo, SAP or inventory systems like Zoho Inventory auto-generate SKUs based on rules you configure. Genfy offers an SKU generator applying standard conventions to speed up manual process.
Duplicate SKUs: the most critical error. If two products share the same SKU, your inventory collapses. Use unique validation in the database and periodic audits.
Redesigning existing SKUs: changing SKU structure in a mature business is expensive: you must update historical orders, integrations and reports. Think through the structure before scaling.
Too generic SKUs: PROD-001 says nothing. When PROD-999 arrives you'll be lost. Include at least the main category.
Confusing SKU with barcode: SKU is internal. UPC/EAN is the barcode scanned at checkout. You can have a product without barcode (handmade goods, for example) but you always need an SKU for internal inventory.
Not documenting the convention: if your team doesn't understand how SKUs are formed, they'll create inconsistent variants. Document the structure in an internal manual or onboarding tool.
Examples
SNE-SPO-NIK-AIRMAX-10-BLK (Sneakers, Sports, Nike Air Max, size 10, black)BOK-TECH-JS-YDKJS-01 (Book, Tech, JavaScript, You Don't Know JS vol 1)TEE-BAS-M-BLU (Basic tee, size M, blue)ACC-USB-C-3M-GRY (Accessory, USB-C cable, 3 meters, gray)B08N5WRWNW (Amazon ASIN, opaque format)
FAQ
Are SKU and barcode the same?
No. Barcode (UPC/EAN) is a global standard identifying a product in any store. SKU is internal: each company defines its own. One product can have a single UPC but different SKUs in different stores.
Can I change SKUs of already-sold products?
Technically yes, but it's risky. Past orders, reports and integrated systems reference the old SKU. If you change it, you need historical mapping or lose traceability. Better keep existing ones and apply new convention only to new products.
How many characters should an SKU have?
Between 6 and 15 characters is most common. Less than 6 limits scalability (you run out of combinations), more than 15 is error-prone. Prioritize clarity over extreme brevity.