SKU (Stock Keeping Unit) is an alphanumeric code a seller assigns to uniquely identify a specific product and its variant attributes for inventory tracking purposes. SKUs are internal identifiers — you define them, you control the format, and they exist in your warehouse management system, not Amazon's catalogue.
SKU vs. ASIN vs. GTIN
| Identifier | Who Creates It | Purpose |
|---|---|---|
| SKU | The seller | Internal inventory tracking |
| ASIN | Amazon | Amazon's catalogue identifier |
| GTIN/UPC | GS1 / manufacturer | Global product identification |
A single ASIN may correspond to multiple seller SKUs (if two sellers carry the same product but use different internal codes). One product in your warehouse has one SKU but may have one ASIN and one UPC.
SKU Best Practices
Encode useful information in the SKU. A well-structured SKU communicates product attributes at a glance. For example: SHOE-NKE-RNR-BLK-10M could represent Shoes / Nike / Runner / Black / Size 10 Men's.
Common attributes to encode:
- Product category abbreviation
- Brand or manufacturer code
- Model/style code
- Colour or variant
- Size (where applicable)
- Condition (new/refurbished)
Keep SKUs consistent. Inconsistent SKU formats make catalogue management, inventory reporting, and repricing tool setup far more difficult as your catalogue grows.
Avoid special characters. Stick to alphanumeric characters, hyphens, and underscores. Slashes, spaces, and symbols can cause issues in Amazon's listing tools and third-party software.
SKUs in Amazon Seller Central
In FBA, your SKU maps to an FNSKU (Fulfillment Network SKU) — Amazon's internal barcode for tracking your specific units through their fulfilment centres. The FNSKU is printed on your product labels when using FBA. Each seller-ASIN combination generates a unique FNSKU, ensuring Amazon can identify your inventory separately from other sellers' identical products.