Free primer · Read anytime before Publish Setup
Understanding ISBNs
You do not have to buy your own ISBN
You will hear strong opinions on both sides of this decision. A free platform-issued ISBN and an ISBN you obtain through your national agency can each suit different publishing plans. Buying one does not automatically make a book better or an author more professional.
Choose based on your plans: for an eligible print edition published only through KDP, its free ISBN may be enough. Your own ISBN gives you control over the imprint and lets you use that ISBN for the same edition through other publishing services. A free KDP ISBN stays with KDP.
You do not have to decide while drafting your manuscript. Make the choice before completing the relevant edition’s publishing setup. Check the rules first—changing an ISBN after publication is not simply editing a number.
Buying an ISBN is optional; needing an ISBN depends on the format and platform. KDP ebooks do not require one, and eligibility for free print ISBNs has exceptions, including low-content books.
Our job is to explain the tradeoffs. The decision is yours.
Compare KDP’s current ISBN options ↗ · Visit Bowker’s MyIdentifiers (U.S.) ↗
What to do
Learn what an ISBN actually is, when your book needs one, and the real tradeoffs between a free ISBN from Amazon KDP and one you buy yourself from Bowker, then use the quick tool below to see which option probably fits your plans.
Why it matters
Your ISBN choice, made once during Publish Setup, is hard to undo later. A free platform ISBN lists that platform as "publisher of record" and generally can't move with you to another platform's print distribution, while an ISBN you buy yourself costs money upfront but is yours to use everywhere. Understanding this now, before you reach Publish Setup, means you won't be guessing under pressure at the moment KDP or IngramSpark asks you to decide.
Step-by-step
- An ISBN (International Standard Book Number) is a unique 13-digit number that identifies one specific edition of a book, in one specific format. Retailers, libraries, and distributors use it to look up and order the exact right version, it's how the book supply chain tells your paperback apart from your hardcover, or your book from every other book.
- Not every book needs one. If you're publishing an ebook only, and distributing it exclusively through a single platform like Amazon KDP, you generally don't need an ISBN at all, KDP assigns its own internal ASIN to track ebooks and doesn't require an ISBN for that. The moment you add a paperback or hardcover edition, or want your ebook distributed "wide" across multiple ebook retailers through an aggregator like Draft2Digital, an ISBN becomes necessary (some wide ebook aggregators require one, others assign their own).
- For print editions (paperback or hardcover), essentially every platform, KDP, IngramSpark, and others, requires an ISBN. You get to choose where that ISBN comes from.
- Option 1: a FREE ISBN from Amazon KDP. Costs nothing, and KDP assigns it automatically when you set up your paperback or hardcover listing. The tradeoff: KDP lists itself ("Independently published") as the publisher of record on that ISBN, not you, and that specific ISBN is tied to KDP, you generally cannot reuse it to list the same edition on IngramSpark, Draft2Digital, or in bookstores and libraries that order through those wider distribution networks.
- Option 2: a PURCHASED ISBN from Bowker, the official U.S. ISBN agency, sold directly at myidentifiers.com. This costs money upfront (a single ISBN is priced noticeably higher per-unit than buying a 10-pack, check Bowker's current pricing before buying). The upside: you, or your own publishing imprint name, are listed as the publisher of record, and that same ISBN can be used for that edition across KDP, IngramSpark, Draft2Digital, and anywhere else you choose to distribute it.
- A helpful shortcut: if you only ever plan to sell print through Amazon and don't care who's listed as "publisher," the free KDP ISBN is simpler and costs nothing. If you want your own imprint listed or plan to use the same edition through multiple publishing services, compare obtaining your own ISBN with the platform-issued options. Choose based on those practical differences and your budget.
- Use the decision tool below for a plain-language recommendation based on your specific plans, then revisit the full step-by-step purchase/assignment instructions in Publish Setup's "Choosing an ISBN" topic when you actually reach that stage.
Which one is probably right for you?
Answer these three quick questions about your own plans. This isn't a purchase, Step One doesn't sell or assign ISBNs, it's just a plain-language pointer based on the tradeoffs above.
Common mistakes to avoid
- Assuming an ebook needs an ISBN, most single-platform ebook publishing (like KDP-exclusive) doesn't require one at all.
- Accepting a free KDP ISBN and then later wanting to distribute the same print edition through IngramSpark or bookstores, that free ISBN generally won't transfer, you'd need a new ISBN (and technically a new edition) to distribute elsewhere.
- Buying an ISBN from a third-party reseller site instead of Bowker's official myidentifiers.com, only Bowker is the legitimate U.S. ISBN agency.
- Buying a single ISBN when you know you'll publish more than one book or format, a 10-pack is almost always better value since paperback and hardcover editions each need their own separate ISBN.
Completion checklist
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Troubleshooting
Can I switch from a free KDP ISBN to my own purchased ISBN later?
Not on the same edition. An ISBN is tied to one specific edition; once KDP has assigned its free ISBN to your paperback listing, that combination is set. If you later want your own publisher-of-record ISBN, you'd typically need to create a new edition (which some authors do, treating it as a "second edition") with a new, purchased ISBN. It's much simpler to decide this before you first publish.
Does Step One sell or assign ISBNs?
No. Step One doesn't sell, issue, or assign ISBNs, we only provide education and this decision tool to help you understand the choice. If you decide to buy your own ISBN, you buy it directly from Bowker at myidentifiers.com, the official U.S. ISBN agency, that's the only place this app links you to for a purchase.
Do I need a different ISBN for my ebook, paperback, and hardcover?
Yes, if each needs one at all. Each distinct format, ebook, paperback, hardcover, audiobook, is treated as its own edition and needs its own separate ISBN (except that many ebook-only, single-platform setups don't need an ISBN at all, see above).