ASINs are implemented in multiple local region editions of Amazon, including the United Kingdom, French, German, Italian, Canadian and Japanese storefronts. Although ASINs used to be unique worldwide, global expansion has changed so that ASINs are only guaranteed unique within a marketplace. The same product may be referred to by several ASINs though, and different national sites may use a different ASIN for the same product. In general, ASINs are likely to be different between the country sites unless they are for a class of product where the ASIN is based on an externally defined and internationally consistent identifier, such as ISBN for books. (Where the ASIN is the same across sites, it is likely to be because the 3rd party creator of the product information was careful to quote an existing ASIN when creating the product in second and subsequent countries, or the subsequent product creation offered exact duplicate information and long enough after the initial creation to allow indexes to have been updated. Also, ISBNs can vary between countries for the same book if a separate print run or edition was published for the country.)
Each product sold on Amazon.com is given a unique ASIN. For books with 10-digit International Standard Book Number (ISBN), the ASIN and the ISBN are the same. The Kindle edition of a book will not use its ISBN as the ASIN.
ASINs are also used for other items used by Amazon.com (and subsidiaries), such as businesses in the yellow pages (on A9.com) and OpenSearch feeds.