You need an ISBN if your book will be available through the book supply chain, meaning bookshops, libraries and wholesalers. You do not need one if it is exclusive to a single platform and sold nowhere else. Self publishing does not decide the answer. Distribution does.
The Actual Rule, From the Agency That Issues Them
The International ISBN Agency's own ISBN Users' Manual states it in one sentence in the section on self publishers:
"If a publication is exclusive to a single platform and not available in the supply chain then an ISBN is not mandatory. However, if the publication is likely to be available in the supply chain (e.g., through booksellers) then it should be assigned an ISBN."
Amazon's KDP arrives at the same place from the other direction, stating that eBooks and low-content books are the only formats where an ISBN is optional. Paperbacks and hardcovers need one because they are physical products that enter distribution.
So the practical answer for most people:
- Ebook, Kindle exclusive, nowhere else. Not required.
- Ebook distributed to Apple, Kobo, Google and libraries. Get one.
- Any print edition. Required, whether you buy it or take a free one.
The Manual is equally clear that in self publishing "the author is treated as the registrant/publisher". You are the publisher. That is not a technicality, it is what an ISBN records.
One ISBN Per Format, Not Per Book
This is the rule that catches people out, and it is stated as a requirement rather than advice: "A separate ISBN shall be assigned to each separate monographic publication or separate edition or format of a monographic publication issued by a publisher."
A novel published as a paperback, a hardback, an EPUB and an audiobook is four ISBNs. If the EPUB is also sold as a PDF, that is five.
The Manual works at three levels of granularity, which the trade press usually flattens into the single word "format":
- Product form, such as hardback, paperback, or downloadable audio.
- Product form detail, such as jacketed hardback, or PDF versus EPUB, or a change of book dimension.
- Product form features, such as a change "from 'normal' text font to dyslexic text font", or EPUB 2 to EPUB 3.
Changes that do trigger a new ISBN include the title, the language, the author name, the publisher or imprint, and "textual content other than minor corrections to misprints".
Changes that do not include a new cover design, a new cover colour, and a change of price. A revised trim size for print on demand is also exempt, since the Manual notes that "minor changes to trim sizes in order to comply with the specifications of on-demand printing machines do not require a new ISBN". A significant change of trim size is a different matter and does need one.
What an ISBN Is Not
Three things people believe that the Manual contradicts directly.
It is not copyright protection. "The ISBN is an identifier and does not convey any form of legal or copyright protection." Registering an ISBN does nothing for your rights.
It is not transferable. A publisher "cannot resell, re-assign, transfer or split its list of ISBNs among other publishers", and agencies may refuse further allocations to registrants who do. You cannot buy a spare from a friend or sell your unused ones.
It is not reusable. "Once assigned to a monographic publication, an ISBN can never be reused to identify another monographic publication, even if the original ISBN is found to have been assigned in error."
Free ISBNs and What They Cost You
KDP, Draft2Digital and IngramSpark will all give you an ISBN at no charge. The tradeoffs are real but narrower than the internet suggests.
Amazon KDP. Free ISBNs "can only be used on KDP. They cannot be used to publish outside of KDP", and the imprint on the book "will appear as 'Independently published'".
Draft2Digital. Assigns one free of charge, and describes the record as showing D2D as "vendor of record", adding that the label "does not give us any rights to your work nor will it show publicly". The same platform lock applies.
Neither arrangement gives the platform any claim on your book. The genuine costs are that the ISBN is unusable elsewhere, and that the publisher of record is not you.
If you buy your own, prices vary sharply by country, and buying a single one is the worst value available. Nielsen's UK store charges £93.00 for one ISBN and £174.00 for a block of ten, so the second through tenth cost less than a pound each. Some countries issue them free, including Canada and France. Buy from the agency for the country you are based in, not the country your platform is in.
What Deckle Does With Your ISBN
Deckle does not have an ISBN field, and this is worth understanding before you go looking for one.
Where your ISBN appears in the book is the copyright page. Deckle's copyright page starts with a placeholder line reading ISBN: [ISBN] for you to replace, alongside a publisher line. That is where the number belongs in a printed book and in an ebook.
For EPUB, the specification requires a unique identifier, and an ISBN is the usual choice for a commercial title. Deckle generates a fresh UUID for that field on each export rather than using your ISBN. The file is valid and every retailer will accept it, because the storefront uses its own record rather than the file's identifier, as explained in ebook metadata explained. If you specifically need the ISBN to be the package identifier, that is an edit to make in the exported file.
The number you enter at the retailer during title setup is the one that matters commercially. Keep it consistent with what is printed on your copyright page, because retailers check.
Common Mistakes
- Assuming self publishing means you need one. The test is supply chain presence, not who published it.
- Using one ISBN across paperback, hardback and ebook. Each format needs its own.
- Buying a single ISBN. In the UK ten cost less than double the price of one.
- Buying from the wrong country's agency. Use the agency for where you are based.
- Expecting an ISBN to protect your copyright. It identifies, nothing more.
- Issuing a new ISBN after fixing typos. Minor corrections to misprints are explicitly exempt.
FAQ
Q: Do I need an ISBN for a Kindle only ebook? A: No. Amazon does not require one and the Agency says it is not mandatory for a single platform publication.
Q: Is the free KDP ISBN bad? A: It is limited rather than bad. It works only on KDP and lists the imprint as "Independently published".
Q: Can I use the same ISBN for the second edition? A: Only if the text is unchanged apart from corrected misprints. Any real revision needs a new one.
Q: Does changing the cover need a new ISBN? A: No. Cover design, cover colour and price changes are all exempt.
Q: Who is listed as the publisher? A: Whoever registered the ISBN. If you bought it, you. If it was free from a platform, that platform's arrangement applies.
Q: How is an ISBN different from an ASIN? A: An ASIN identifies a product inside Amazon's catalogue only. See ISBN vs ASIN.