Selling Your Book

What is an ISBN? Everything You Need to Know About The International Standard Book Number

If you’ve been even remotely interested in books for any significant length of time, you’ve probably heard of the International Standard Book Number or ISBN. But what is an ISBN? We get a lot of questions about this from our users, so in this blog post, we’re going to examine these inconspicuous bar codes in detail.

So What is an ISBN Exactly?

A Brief History

The ISBN was first conceptualized by David Whitaker in 1967 and then developed by the International Standardization Organization (ISO). The result was the 10-digit ISBN code, published in 1970. Following its publication, the International ISBN Agency was given the authority to distribute the new code worldwide.

In the UK, the predecessor to the ISBN – the Standard Book Numbering (SBN) code – remained in use until 1974. As such, there are still a fair number of SBN-marked books still in circulation. In order to convert an SBN to an ISBN, a 0 is added at the beginning of the code.

With the number of books published rising exponentially in the decades following the launch of the 10-digit ISBN, the International ISBN Agency was running out of codes quicker than anticipated. As such, the length of an ISBN code was increased to 13 digits in 2007.

How Does it Work?

In essence, an ISBN is just a product code, much like any bar code you might see on items in your local grocery store. If a book has an ISBN, it becomes internationally recognizable (and thus sellable) in any store that sells books, whether it be physical or online.

Each ISBN is unique to the edition and variation of a particular book. As such, if one were to publish the same book in hardcover, paperback, and e-book formats, each of these three variations would require a different ISBN number. This is due to the fact that they are different products, legally and physically speaking, even if the content is the same.

Similarly, if one were to publish an updated edition of a published book, with e.g. extra chapters or a different foreword, this too would require a new ISBN. While this may be annoying for self-published authors, the vast number of books in circulation makes it necessary.

What do the Numbers in an ISBN Code Actually Mean?

ISBN code issued by Mybestseller

The bar code above is an ISBN issued by Bookmundo which we’re going to use as an example. Keep in mind that ISBN numbers may look slightly different depending on the publisher or retailer that issued them. For example, some versions will have a hyphenated version of the code on top of the bars, whereas in other versions this is replaced by the price of the book. So if your ISBN doesn’t look exactly like the one on the book you happen to be reading at the moment – don’t worry! It’s completely normal. As long as the number sequence at the bottom contains 13 digits, you’re good to go!

Now, let’s take a closer look at those 13 digits in an ISBN:

What is an ISBN - components


The first three numbers of an ISBN are always either 978 or 979. These are the numbers made available by GS1 (the organization that issues bar codes). Essentially, it serves to identify the product in question as being a book.


The group identifier specifies the language group, country, or region that the book belongs to.


Identifies the publisher of the book. Larger publishers may have more than one number associated with them.


This sequence identifies the specific title associated with this particular ISBN.

Check Digit

A check digit is a form of error control for publishers, retailers, and institutions to verify an ISBN. As such, it doesn’t provide you as an author with any meaningful information.

Placement of the ISBN

The ISBN User’s Manual has the following to say regarding the placement of an ISBN code:

In the case of printed publications, the ISBN must appear on the:

  • Verso of the title page (copyright page)
  • Foot of the title page, if there is no space on the title verso
  • Lower section of the outside back cover
  • Foot of the back of the jacket, or any other protective case, or wrapper

In the case of digital publications, the ISBN must appear on the:

  • Title display; the first display (compact discs, online publications); or on the screen that displays the title or its equivalent (e.g., the initial screen displayed when the content is first accessed and/or on the screen that carries the copyright notice)

Furthermore, the manual states that the code must be printed/displayed in type large enough to be legible; specifically 9-point or larger.

This isn’t something that you have to worry about if you publish with us though. When purchasing an ISBN for your book via our platform, we automatically place the code in the correct places, appropriately sized.

Do I Really Need an ISBN?

Short answer? No.

You do not need an ISBN number to publish or print your book. Its only purpose is to make it easier to stock and sell books, and you technically don’t even need one to do that. You could for example print copies of your books to sell in person or just sell your books via your own website rather than a third-party retailer. If you publish your book with Bookmundo, you also won’t need an ISBN number to sell your book in our online book store.

However, if your ambition is to earn money with your books, it’s advisable to get an ISBN. The sales channels that become available to you with an ISBN offer more potential reach than you could ever hope to achieve on your own. This allows people to find your book without you having to direct them to it yourself. Furthermore, people like shopping in stores whose brand they recognize. The fact that your book is available there will boost your legitimacy as a writer.

Nevertheless, whenever possible, you should strive to get people to buy your book from you directly, or via the Bookmundo store. This nets you the highest possible profit margin per copy – for each book, you sell via our store, you’ll have to sell at least two via a third party. You can create widgets on our website for free to facilitate these sales.

Acquiring an ISBN

If you’re looking to buy an ISBN, you can do so while publishing your book on our platform – without missing a beat – for £12.75. You’ll receive it right away, and it will automatically be placed in all the necessary places as listed above.

Additionally, you will of course gain direct access to all of our retail partners, without having to create an account with each one individually. Furthermore, all the sales figures and other relevant data from these sales channels will be compiled in the Bookmundo interface. As such, you’ll get a handy overview of your book sales across all the sales channels through which your book is sold.

Alright – we’re done tooting our own horn now, we promise! If you’re not publishing your book with us, but simply wanted to read a comprehensive article about ISBNs, that’s obviously fine as well. Should you want to acquire an ISBN somewhere else, then we recommend getting in touch with your publisher. Often, publishers won’t accept ISBN codes acquired through other publishers, as it messes with their databases. In other words, it’s probably a good idea to decide how and where you want to publish your book before buying an ISBN.

Final Note

That’s all for this time around folks. We hope this article addressed any unanswered questions you might have had about ISBNs. If there’s anything you’d like us to elaborate on or add, feel free to let us know in the comments or in an email. You can find some more info about ISBNs on our FAQ page.