ISBN vs ASIN
An ISBN and an ASIN both identify a book, but they come from different systems and do different jobs.
- An ISBN is a 13-digit number from a national ISBN agency. It identifies one edition and format of a book across the book trade: retailers, distributors, wholesalers and libraries.
- An ASIN is a 10-character code Amazon assigns to every product in its own catalog. It means nothing outside Amazon.
A book on Amazon can have both. A KDP paperback has an ISBN (your own or KDP’s free one), and Amazon also gives it an ASIN. A Kindle ebook usually has only an ASIN, because KDP doesn’t require an ISBN for ebooks.
Why it matters for indie authors
The difference decides what you need to obtain and where your book can go.
| ISBN | ASIN | |
|---|---|---|
| Issued by | A national ISBN agency, or KDP’s free option for print | Amazon, automatically |
| Recognized | Across the book trade | On Amazon only |
| Needed for | Print books, and ebooks with some distributors | Every product Amazon sells |
| Cost | Varies by country; free in some | Free |
If you only sell ebooks on Amazon, the ASIN is enough. Once you print, sell in other stores or want libraries and bookstores to order your book, ISBNs come into play, and who owns them matters.
Example
A romance author publishes on KDP only. Her Kindle edition gets an ASIN and no ISBN. For the paperback she accepts KDP’s free ISBN, and Amazon gives the paperback its own ASIN as well. A year later she wants the paperback available to bookstores through another distributor. The free KDP ISBN can’t be used outside KDP, so she buys her own ISBN and sets up that edition with it.
Common mistakes
- Buying an ISBN for an ebook you’ll only sell on Kindle, where it’s optional.
- Using an ASIN outside Amazon, for example on a copyright page or in a listing for libraries. It isn’t recognized there.
- Mixing up identifiers in links and ads. Amazon links and Amazon Ads work with the ASIN of each specific format.
- Forgetting that every format needs its own identifiers. The paperback, hardcover and ebook each have their own ASIN, and each print format needs its own ISBN.