Other Item Identifiers

Amazon has other item identifiers but these are rarer and they can be used in fewer Amazon Associates Web Service operations:

UPC—(Universal Product Code) A 12-digit item identifier used in the US and CA locales. The UPC is identifier used in barcodes.
EAN—(European Article Number) A 13-digit equivalent of the UPC that is used in Europe for products and barcodes.
JAN—(Japanese Article Number) The equivalent of the EAN that is used in Japan for products and barcodes.
ISBN—(International Standardized Book Number) An alphanumeric token that uniquely identifies a book. A book's EAN is typically set equal to the book's ISBN.
SKU—(Stock Keeping Unit ) A merchant-specific identifier for a purchasable good, like a shirt or chair. Amazon's version of the SKU is the ASIN.
Amazon assigns items with SKUs an ASIN. If you had to search by SKU only, you would have to search each merchant's items independently because SKUs are not unique across all merchants. Several Amazon Associates Web Service operations enable you to search by SKU but the merchant must also be identified in the same request.

All items in the Amazon marketplace have an ASIN even if they also have one of the identifiers listed above. Only a few Amazon Associates Web Service operations can use these identifiers. That functionality is presented as a convenience function. You would typically only use one of these identifiers if you knew it but did not know the item's ASIN.