What Is An ISBN?

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Carina Pereira

Staff Writer

Carina Pereira, born in ‘87, in Portugal. Moved to Belgium in 2011, and to Rotterdam, The Netherlands, in 2019. Avid reader, changing interests as the mods strikes. Whiles away the time by improvising stand-up routines she’ll never get to perform. Books are a life-long affair, audiobooks a life-changing discovery of adulthood. Selling books by day, writer by night. Contact

Have you ever stumbled upon the letters ISBN when people talk about book stuff, and always wondered what exactly an ISBN is, but you were always too lazy – or forgetful, no judgment here – to google it and find out?

Fear not! ISBN doing some research, and I am about to explain to you exactly what those numbers on the back of your books mean. So buckle up, enjoy that pun – which, yes, I absolutely needed to make – and let me take you on a little ride down ISBN history lane. 

What Does ISBN Stand For And Why Do We Use It?

Let’s begin at the root of the initialism: ISBN stands for International Standard Book Number, and as its full name reveals, it was created with the intent to standardise the way we identify books across the world.

If you are ever looking to buy a specific edition of a book, that book’s ISBN is your best friend. Equally, if you are requesting the help of a bookseller while finding said book, providing them with an ISBN will not only make their life easier, it will assure you get exactly the book and edition you are looking for.

Remember when people were buying Randall Hansen’s Fire and Fury in mass, instead of Michael Wolff’s book on Trump? This could have been avoided if 1) people knew what to look for exactly, and 2) if they had had the ISBN of the book in the first place. The only way you can get it wrong with an ISBN is, of course, if you have the wrong ISBN.

Every edition of a book gets its own ISBN, meaning that ebooks, audiobooks, hardbacks, and paperbacks – and books with different covers or sizes, or translations – will have a different ISBN. The only exception to this rule is for reprints.

In simple terms, ISBNs are like IDs for books.

A Little Bit Of History

I thrive in neat and organised environments, so it is a joy to see other fellow humans doing their best to create a world where organisation is key, making life easier for all of us. I really can’t imagine the chaos it would be to work in publishing, or in any job which deals with books so closely, without a number to make them easier to identify.

In bookstores, we already get people on the regular asking for “that book with a blue cover, which is none of the books with a blue cover you have in the shop, but maybe you know which book I’m looking for?” so anything that can make books easier to find is a blessing.

Here it is then, my personal appreciation for Gordon Foster, for creating the first Standard Book Number system (SBN) in 1965. Commissioned to create a filling system by WH Smith, a British retailer, Foster paved the way and put his back into what would later become the ISBN.

The ISBN was created two years later, by David Whitaker, and began to be used in the United States in 1968, developed by Emery Koltay. It was a standard nine digits.

This caught the attention of the ISO (International Organisation for Standardization), and after a few meetings with executives across Europe, it was decided to implement the system on a global scale.

The ISBN became standard in 1970, with a ten-digit format, and is now used in over 150 countries.

Much later, in 2007, books started to contain 13 digits, an effort to make them compatible with the International Article Number (or European Article Number, which you might have stumbled upon under EAN), that you find in barcodes. This means that books with an ISBN assigned after 2007 will all have 13 digits.

But, Carina, you ask, what happened to the nine-digit SBNs, and how did they make up a 13-digit ISBN from a ten-digit one? Simple: to all nine-digit SBNs was added a prefix 0, and an EAN prefix (usually 978) was added to the ten-digit ISBN, completing the 13-digit ISBN we currently use.

But What Do The Numbers Mean?

Each ISBN (published after January 2007), contains five elements: EAN prefix, registration group element, registrant element, publication element, and a check digit. This is what each of these groups of words mean:

EAN prefix: the international article number (for books that is currently 978 or 979 – check the following link if you want to find out what Bookland is);

Registration group element: identifies a national or geographical grouping of publishers;

Registrant Element: identifies the publisher;

Publication element: identifies a particular title or edition;

Check digit: I have to admit that when I first read the definition for check digit, I didn’t understand a thing. Here is the quote: “check digit is always the final single digit that mathematically validates the rest of the number. It is calculated using a Modulus 10 system with alternate weights of 1 and 3.”

I understand the words in it individually, but not as a whole, especially the second sentence there.

Wikipedia has a long-ass section explaining check digits, which only confused me further, but after a bit of research, I ended understanding that this is a number meant to detect errors and avoid redundancy. This is also the reason why some ISBNs contain an X at the end.

I mean, personally, I don’t really understand what the point of the X is exactly, but I’m okay with my ignorance in this matter. If you’d like to find more – and brace yourself for some mathematics – check the last link above.

(Yes, I am a Humanities student, why do you ask?)

Where Do I Find The ISBN?

Although this can vary from book to book, there are usually two places where you can find the ISBN: on the copyright page (usually second or third page of the book), and on the back cover, either on the barcode or just printed onto the cover – sometimes both.

As a bookseller, I must admit I have stumbled upon books where the ISBN is not in its usual place, and it feels a bit like a treasure hunt to try and find it. But it’s always there.

I’m An Author And I Want To Publish A Book. Do I Need An ISBN?

While ISBNs are not a form of copyrighting in any way, some countries require books to be legally identified by an ISBN.

If you’re taking the traditional route and getting your book out in the world through a publishing house, an ISBN will be attributed to your book by the publisher.

When you self-publish and sell online, you have the option to use an ISBN provided by the company that owns the website you are using to sell your ebooks. But do you really need an ISBN to sell a self-published book? Depends on where you want to sell it, and what exactly you are trying to achieve with your book.

Amazon, Barnes & Noble, Kobo, and Apple do not require your ebook to have an ISBN in order to be sold online, but if you want to sell physical copies to retailers, libraries, and bookstores, you will need to get one.

The advantage of getting your own ISBN, even for ebooks, rather than using one provided by a website, is that you can keep it even if you change platforms.

ISBNs are also super helpful when it comes to unmarketed sales, because it makes your book easier to find through its metadata, and it makes it more likely to be shared. Trust me, book people like ISBNs.

If you are self-publishing an ebook, you can certainly skip the ISBN and save that money for something else. If the sales end up being so good that you decide it’s worth printing it, or selling it on other platforms which require an ISBN, you can always get an ISBN later.

You can find a database of all agencies selling ISBNs worldwide at the International ISBN Agency website. 

Now, if you’ll excuse me, I have a blue cover book to find.

For more book anatomy, check out this guide to the parts of a book. If you have enjoyed the pun at the beginning of this article, check out this cool Book Riot x Out Of Print ISBN Thinking of You T-shirt (and more).

Red shirt with text reading "ISBN Thinking of You"


International ISBN Agency

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