What Is a Book’s ISBN, and Do I Need One for KDP?

 An ISBN is a vital identifier in the publishing world. If you’re planning to publish a book through Amazon’s Kindle Direct Publishing (KDP), you’ve likely come across this term. But what exactly is an ISBN? Do you need one for your eBook or paperback on KDP? Can you use your own, or should you accept Amazon’s free one?

This article answers these questions and more. We’ll explain what an ISBN is, how it works, whether it’s mandatory for KDP publishing, and how to decide which type of ISBN is right for you.

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What Is an ISBN?

ISBN stands for International Standard Book Number. It’s a 13-digit unique identifier assigned to books and other monographic publications. Think of it like a fingerprint for your book—no two ISBNs are the same, and each one corresponds to a specific edition and format of a book.

The ISBN system was created to:

• Help publishers, libraries, retailers, and distributors identify books accurately

• Streamline ordering and inventory processes

• Distinguish between different versions of the same book (e.g., eBook, paperback, hardcover, audiobook)

A single book may have multiple ISBNs:

• One for the paperback edition

• One for the eBook

• One for the audiobook

• One for the hardcover

Each format requires a different ISBN.

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What Does an ISBN Look Like?

A modern ISBN is 13 digits and is typically displayed like this:

ISBN 978-1-234567-89-0

It is often printed on the back cover above the barcode, inside the copyright page, and listed in online retail metadata.

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Who Assigns ISBNs?

ISBNs are assigned by official agencies designated by the International ISBN Agency, headquartered in London. Each country or region has its own agency:

• United States: Bowker (www.myidentifiers.com)

• UK: Nielsen UK ISBN Agency

• Canada: Library and Archives Canada (free to Canadian residents)

• Kenya: Kenya National Library Service (KNLS)

• India: Raja Rammohun Roy Library Foundation (free)

Authors or publishers purchase ISBNs directly from these agencies or receive them from publishing services like Amazon, IngramSpark, or others.

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Do You Need an ISBN for KDP?

The need for an ISBN on Amazon’s KDP platform depends on the book format:

✅ eBook (Kindle Format) – No ISBN Required

• Amazon assigns its own identifier called an ASIN (Amazon Standard Identification Number).

• You do not need an ISBN to publish a Kindle eBook.

• If you already have an ISBN, you can include it, but it’s optional and not used in Amazon’s system.

Key Point: ISBNs are not mandatory for Kindle eBooks on Amazon.

✅ Paperback (Print Version) – ISBN Required

• Amazon requires an ISBN for paperbacks.

• You have two options:

  1. Use Amazon’s free ISBN

  2. Provide your own ISBN purchased from an official agency

Let’s break down both options.

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Option 1: Using Amazon’s Free ISBN (for Paperback)

When uploading your paperback to KDP, you can choose to have Amazon assign you a free ISBN. This ISBN allows your book to be sold on Amazon and printed via KDP’s print-on-demand service.

Advantages:

• Completely free

• Quick and easy to obtain

• No need to register or pay a third-party agency

Limitations:

• Amazon (not you) is listed as the publisher of record.

• You cannot use the ISBN outside of Amazon (e.g., to print through IngramSpark or distribute to bookstores).

• It’s tied exclusively to the KDP platform.

Best for: Authors who only plan to publish on Amazon and don’t care about owning their publishing imprint.

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Option 2: Providing Your Own ISBN (for Paperback)

If you want full publishing control, you can purchase your own ISBN from your local ISBN agency and use it on KDP.

Advantages:

• You or your imprint is listed as the publisher.

• You can use the same ISBN to publish the book on multiple platforms (e.g., Amazon, IngramSpark, Draft2Digital Print).

• Offers more professional branding, especially for authors building a publishing business.

Limitations:

• ISBNs can be expensive (in the U.S., a single ISBN costs about $125; bulk purchases reduce the cost per unit).

• Requires setup with a national ISBN agency.

Best for: Authors who plan to publish widely across platforms, want to control their metadata, or intend to create a publishing imprint.

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What Happens If You Publish the Same Book in Multiple Formats?

You’ll need a separate ISBN for each edition and format of your book:

• eBook (optional or unused on Amazon, mandatory for other platforms like Apple Books or Kobo)

• Paperback

• Hardcover

• Audiobook

Even slight differences in formatting (e.g., large print or revised edition) require a new ISBN.

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What About Barcodes?

KDP automatically generates a barcode for your paperback, whether you use their free ISBN or your own. You do not need to upload your own barcode unless you are using a cover template that includes one.

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ISBNs and Expanded Distribution

If you plan to enroll your paperback in Expanded Distribution (allowing it to be sold to libraries and bookstores outside Amazon), ISBN ownership becomes more important.

• You can use Amazon’s free ISBN for Expanded Distribution, but:

  • Some retailers and libraries may not accept books with an Amazon-owned ISBN.

  • It limits your ability to control listings in broader distribution channels.

Owning your ISBN makes your book more versatile and credible in the wider publishing ecosystem.

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ISBN vs. ASIN: What’s the Difference?

Feature	ISBN	ASIN
Stands for	International Standard Book Number	Amazon Standard Identification Number
Length	13 digits	10-character alphanumeric
Use	Used globally across retailers	Used only within Amazon
Assigned by	ISBN agency (Bowker, Nielsen, etc.)	Automatically by Amazon
Required for eBooks	Optional on Amazon	Yes (automatically assigned)
Required for Print	Yes	No

Should You Buy Your Own ISBN or Use Amazon’s Free One?

Here’s a quick comparison to help you decide:

Criteria	Use Free ISBN	Buy Your Own ISBN
Budget-conscious or just starting	✅ Yes	❌ Not ideal unless you invest
Want to publish ONLY on Amazon	✅ Yes	❌ Not necessary
Want to be listed as the publisher	❌ No (Amazon is listed)	✅ Yes
Plan to publish wide (multiple stores)	❌ Limited	✅ Necessary for flexibility
Building a professional author brand	❌ Less control	✅ Full control

Conclusion

An ISBN is a critical identifier for published books, especially in print. If you’re publishing a Kindle eBook, you do not need an ISBN on Amazon. However, if you’re publishing a paperback, KDP requires one—and you can choose to use Amazon’s free ISBN or provide your own.

Using Amazon’s free ISBN is sufficient for many self-publishers, especially beginners who plan to sell exclusively on Amazon. But if you’re building a publishing brand, want greater distribution, or need to control how your book is listed across platforms, investing in your own ISBNs is a smart long-term strategy.

In the world of self-publishing, owning your ISBN means owning your publishing identity. Decide based on your goals, budget, and publishing vision.