An ISBN, or International Standard Book Number, is a 13-digit number that identifies one edition of a book in one format. You do not need an ISBN to sell a Kindle eBook on Amazon, but you do need one to sell a print book through most retailers and distributors, and many authors choose to buy their own so they remain the publisher of record. Each format, such as paperback, hardcover and eBook, needs its own number.
This guide explains what an ISBN does, how free and purchased numbers differ, when you can skip one and how to register without wasting money. If you want help, we offer ISBN and copyright registration. To see where an ISBN fits in the publishing process, read how to publish a book on Amazon KDP.
Key takeaways
- An ISBN identifies a specific edition and format of a book
- Each format and each new edition needs its own ISBN
- KDP offers free ISBNs for print, but they name KDP as the publisher and cannot be used elsewhere
- Buying your own ISBNs makes you the publisher of record and lets you use them across stores
- An ISBN is not a copyright; copyright is separate
In this article
- What is an ISBN used for?
- Do I need an ISBN for every format?
- How do free ISBNs from KDP differ from buying your own?
- Do I need an ISBN for an eBook?
- How do I buy and register an ISBN?
- Is an ISBN the same as copyright?
- What mistakes should I avoid with ISBNs?
- What about large print, audiobooks and later editions?
- Frequently asked questions
- Services that can help
What is an ISBN used for?
Bookstores, libraries, distributors and retailers use ISBNs to order, track and catalogue books. The number links to details such as title, author, publisher, format and price, so a bookshop can order the right edition and a library can find it. The ISBN also appears in the barcode on the back of a print book. Without one, a print book is hard to sell through wholesale channels or to place in bookshops and libraries.
Do I need an ISBN for every format?
Yes. A paperback, a hardcover, a large print edition and an eBook are different products and each should have a different ISBN. A revised edition with significant changes also needs a new one, while a small correction usually does not. Audiobooks have their own ISBNs as well. Using one number for several formats confuses retailers and can cause listings to merge or break. Our Amazon listing fixes service often repairs problems that start with reused ISBNs.
How do free ISBNs from KDP differ from buying your own?
A free KDP ISBN costs nothing, but it names KDP as the publisher and can be used only for that edition on that platform. If you later want to publish the same edition through another printer or distributor, you need a different ISBN, which can split your reviews and records. Buying your own ISBN means you are listed as the publisher, you can use the number wherever you publish and you control the metadata. In the United States, ISBNs are sold by one national agency, and in many other countries the national agency issues them free or at low cost, so check your own country.
Do I need an ISBN for an eBook?
Not on Amazon, which uses its own identifier for Kindle eBooks. Many other eBook retailers also do not require one. An ISBN can still help with libraries, some distributors and consistent records across stores, so some authors register one for the eBook anyway. If you plan to go wide, plan your ISBNs before you publish, because changing them later can disturb listings. See our guide to publishing on Amazon KDP for the Amazon side.
How do I buy and register an ISBN?
- Find your national ISBN agency, which is the only official source in each country
- Buy a single ISBN or a block, and buy a block if you plan several formats or books
- Assign each number to a specific format and edition
- Enter the publisher name and book details in the agency’s system
- Use the same details on the copyright page, the barcode and every retailer listing
Be careful with resellers who sell individual numbers at a premium, since the publisher listed may not be you.
Is an ISBN the same as copyright?
No. An ISBN identifies a book edition for sales and cataloguing, while copyright is the legal right to your creative work. Copyright arises automatically when you create the work in most countries, and registration with a national office adds extra legal benefits where it is available. You can have an ISBN without registering copyright and the reverse. We explain the difference in our ISBN and copyright registration service.
What mistakes should I avoid with ISBNs?
Most ISBN problems come from small slips made early, and they are expensive to fix once books are listed.
- Reusing one ISBN across several formats or editions
- Buying from a reseller and finding that the publisher listed is not you
- Changing the ISBN after launch, which can split reviews and records
- Forgetting to update the copyright page and barcode when the number changes
- Assigning numbers before you know which formats you will publish
What about large print, audiobooks and later editions?
A large print edition, an audiobook and a revised edition each need their own ISBN. Keep a simple spreadsheet that records each number, the format, the edition, the date and where it is used. It prevents duplicates, helps you answer retailers and makes it easy to explain your catalogue to a distributor or an accountant.
Frequently asked questions
How much does an ISBN cost?
It depends on your country. Some national agencies issue them free, while others sell single numbers and blocks, and blocks are usually cheaper per number.
Can I use one ISBN for my paperback and hardcover?
No. Each format needs its own number, or retailers will confuse the editions.
Can I change the ISBN after publishing?
You can, but it can disturb reviews and listings. It is better to choose correctly before you publish.
Do I need a barcode?
Print books sold in shops need one that encodes the ISBN. Platforms such as KDP can generate it, or you can supply your own.
What happens if I publish without an ISBN?
You can still sell eBooks on Amazon, but print books and wider distribution generally need one, and some listing features may be limited.
Who is the publisher if I use my own ISBN?
You are, under the name you register. Many authors register a small imprint name for a more professional look.
Services that can help
- ISBN and copyright registration
- Self-publishing services
- KDP account setup
- Amazon book listing fixes
- Book distribution services
This guide is part of our book publishing guides and connects to our book publishing services.