An ISBN identifies a publication across the entire book trade, is issued under an international standard, and belongs to whoever registered it. An ASIN identifies a product inside Amazon's catalogue, is assigned by Amazon, and means nothing anywhere else. You apply for one. The other simply appears.
The Difference That Matters
| ISBN | ASIN | |
|---|---|---|
| Stands for | International Standard Book Number | Amazon Standard Identification Number |
| Issued by | A national ISBN agency, under the International ISBN Agency | Amazon |
| Governed by | ISO 2108 | Amazon's catalogue rules |
| Scope | The whole book supply chain: shops, libraries, wholesalers | Amazon only |
| Who obtains it | The publisher, which for a self published book is you | Nobody, it is assigned automatically |
| Cost | Varies by country, free in some | None |
| Applies to | Books | Every product Amazon sells |
| Transferable | No, never reassigned or reused | Not applicable |
Amazon's own developer documentation defines an ASIN as a unique number that identifies an item in the Amazon catalog. That is the whole definition, and the phrase "in the Amazon catalog" is the entire point. It is a catalogue key, not a publishing identifier.
The International ISBN Agency describes the ISBN as an identifier for monographic publications issued under ISO 2108, thirteen digits since January 2007, with a check digit calculated by formula. It notes that in some countries the use of ISBN has been made a legal requirement.
They Do Not Replace Each Other
Every book listed on Amazon has an ASIN, whether or not it has an ISBN. If your book has an ISBN, it still gets an ASIN, because Amazon needs its own catalogue key.
You will see the ASIN on the product page and in the URL. You will not see it anywhere else. Send an ASIN to a bookshop, a library or a distributor and it means nothing to them, because they run on ISBN.
This is the practical consequence: an ASIN cannot get your book into a bookshop. If a bookseller, a library or a wholesaler is anywhere in your plans, the question is not ISBN versus ASIN, it is whether you have an ISBN at all. That question is answered in do I need an ISBN to self publish.
The ISBN-10 Question
A claim repeated almost everywhere is that for books, the ASIN simply is the ISBN-10. It appears to be broadly true in practice for titles that carry an ISBN, but it is worth being precise: this is not stated in any Amazon documentation reachable at the time of writing, and Amazon's own definition of ASIN says nothing about ISBNs.
Treat it as an observed pattern, not a rule. Do not build anything on it, and never give an ASIN where an ISBN is asked for, even if the digits happen to match.
Which One Goes on Your Copyright Page
The ISBN, and only the ISBN. An ASIN is a retailer's internal reference and has no place inside the book. If you publish in several formats, the convention is to list the ISBN for each one on the copyright page, labelled by format.
The same applies to file metadata. The identifier inside an EPUB is meant to be a publication identifier, which in a commercial book usually means the ISBN. It is never an ASIN.
What Deckle Does
Deckle has no ISBN field and no ASIN field, because neither is something the writing application needs to know.
Your ISBN goes on the copyright page, and Deckle's copyright page preset starts with a placeholder line reading ISBN: [ISBN] alongside a publisher line, ready to be replaced with your own. That is the correct home for it in both print and ebook editions.
For EPUB, the specification requires a unique identifier in the package document. Deckle generates a UUID for that field rather than using an ISBN, which produces a valid file that every retailer accepts, since storefronts use their own metadata record rather than the file's identifier. The distinction between the two records is covered in ebook metadata explained.
Your ASIN is created by Amazon after you publish. There is nothing to enter anywhere, in Deckle or otherwise.
Common Mistakes
- Giving an ASIN to a bookshop or library. It is meaningless outside Amazon.
- Assuming an ASIN means you do not need an ISBN. It is a catalogue key, not a trade identifier.
- Printing an ASIN on the copyright page. Only ISBNs belong there.
- Treating the ASIN as your ISBN-10. They frequently coincide. That is not the same as being interchangeable.
- Expecting a stable ASIN. It belongs to Amazon's catalogue and is theirs to manage, not yours.
FAQ
Q: Does my book get an ASIN automatically? A: Yes. Amazon assigns one to every item in its catalogue, with or without an ISBN.
Q: Can I choose my own ASIN? A: No. Amazon assigns it.
Q: Do I need both? A: You never obtain an ASIN, so the only decision is the ISBN. Whether you need one depends on whether the book enters the supply chain.
Q: Is an ASIN unique worldwide? A: It is unique within Amazon's catalogue, which is the only place it applies.
Q: My paperback and ebook have different ASINs. Is that wrong? A: No. Different products get different ASINs, exactly as they get different ISBNs.