ASIN Defined.
Definition
An ASIN (Amazon Standard Identification Number) is the 10-character code Amazon assigns to every product in its catalog. Each edition of a book sold on Amazon has its own, the Kindle ebook and the paperback alike. It identifies the product only inside Amazon: unlike an ISBN, it means nothing to other bookstores or library catalogs.
Sources checked 20 October 2026.
How it works
Amazon creates an ASIN whenever a new product detail page is made, so publishing an ebook on KDP gives it one without your asking. You can read it in two places: in the page address, after /dp/, and in the product details section of the page. Because a Kindle ebook needs no ISBN on KDP, its ASIN is often the only identifier it has. ASINs matter for reviews too: KDP says customer reviews are shared across marketplaces only where the same book's ASIN and format are live.
An example
You run an ad for the Kindle edition and link to its page. The link should carry the ebook's ASIN after /dp/; the paperback's page has a different code, since every product gets a unique one, so a link built from the paperback's address sends readers to the print edition instead.
Common mistakes
Giving an ASIN where another retailer or a library asks for an ISBN: outside Amazon it identifies nothing. Assuming the ebook and paperback share one code. And buying an ISBN for a Kindle ebook only to get it listed: KDP says an ISBN is optional for ebooks, and Amazon assigns the ASIN either way.
