What is an ISBN?

Owning your own ISBNs gives you publishing freedom. You will never be locked into a service and you are in charge of the information that is distributed to the bookstores. So, in this lesson, you’ll learn what an ISBN is and what each set of numbers means. You're going to need a packet of 10 or 100 ISBNs to assign to the various formats of your book: paperback, hardback, EPUB, MOBI for Amazon Kindle, and audiobook. (You'll learn more about formats and prices in a later lesson.)

The International Standard Book Number (ISBN) system was created to assign a unique identifier to every published book.

Whoever owns the ISBN to your book is the publisher of the book, so it should be you.

The numbers

ISBNs consist of 13 numbers. Here’s what you need to know about these numbers.

  • EAN Prefix: Currently either 978 or 979, this identifies the EAN element (European/International Article Number) and tells cashiers that this is a book rather than another kind of product like food or a toy.
  • Registration group: Identifies the country or language agency.
  • Registrant or Publisher Identifier: Numbers 6-9 makes up the four numbers of your publisher identifier, which identifies you and your publishing company. (You’ll need this number when applying for a PCN, LCCN and a CIP block for libraries. You’ll learn about this stuff later.)
  • Title: The particular edition and format of your book. (hardback, paperback, EPUB, Kindle, audio, etc.)
  • Check digit: The check digit is a mathematical validation of the ISBN. In plain English this means it has been verified (it's real!) by the powers that be that oversee ISBNs.

Do you need them?

Do you really need an ISBN?

No. Yes. Maybe.

Bear with me.

ISBNs in the US are expensive—$295 for a set of ten. In other countries, they are much more affordable, and may even free.

Technically, you don’t actually need an ISBN for your ebook if you upload it to each online retailer directly (for example, Amazon, B&N, Kobo). But as an independent author publishing professionally, you should definitely assign an ISBN to every book.

You are required to assign an ISBN to books that use a distributor (IngramSpark, Smashwords) to reach the online retailers and bricks-and-mortar bookstores.

ISBNs vs product numbers

The online retailers assign their own "product" numbers to every product they sell, and books are a product. They will also list your ISBN. For example, Amazon uses an ASIN (Amazon Standard Identification Number).

If you don't own your own ISBNs, then Amazon CreateSpace, IngramSpark, and other vendors will happily supply them for you. But the ISBNs they give you are associated with the company that owns them. So don't do it. As a publishing professional, that company should be you.


Use one ISBN to identify your paperback book, no matter where it's sold, and another to identify the hardback edition, no matter where it's sold, and another to identify the EPUB version, no matter where it's sold, and another to identify the audiobook version, no matter where it's sold, and another for the MOBI for Kindle version, no matter where it's sold.

You'll find out more about assigning ISBNs to formats just a couple of lessons from now but take a look at this short video by Julie Rodd, a Canadian author and marketing pro, for a review of what you're learning in this lesson plus an insight that surprised me about the marketing strategy behind releasing one format at a time.


When you own your ISBNs you are an independent publisher. That means you are in control of your book and it is portable among vendors and distribution and printing companies.

If you want to look like a modest publishing house and not a self-published author, buy a block of 100 ISBNs.

You'll learn more about pricing and how to purchase ISBNs in another lesson of this module.

How many ISBNs do you really need?

If you write more than three books, you'll need more than 10 ISBNs, that is, if you are publishing in hardback, paperback, EPUB, MOBI, and audiobook formats.

An author of a series of three books will need, at minimum, 9 ISBNs, but add 3 more if you do an audiobook. That's 12! So buy that bundle of 100 ISBNs.

  • 3 ISBNs for the paperback editions
  • 3 ISBNs for the EPUB format
  • 3 ISBNs for the MOBI for Amazon Kindle format
  • 3 ISBNs for the audiobook

Do you need a SAN?

When you’re purchasing ISBNs you may see the opportunity to purchase a SAN. A Standard Address Number, or SAN, is useful if you become a small press by publishing other authors and grow so large that ordering systems get confused. A SAN helps to reduce billing errors, books shipped to the wrong points, and errors in payments and returns. Most self-publishers don’t need a SAN.

What's next?

Learn more about why it’s important to purchase your own ISBNs instead of using a free ISBN from a publishing services company in the next lesson.