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In part 1 of this series, A Primer on ISBNs, I covered a lot of the general information around these ubiquitous identifiers. If you missed it, click over to that post and learn what they are, what they’re used for, and a host of other ISBN basics. In today’s post, I’m going to go more in depth about ISBN usage. And, again, I will be pulling in data directly from R.R. Bowker (, the official registration agency for ISBNs within the United States.

To make this easier to follow, I am going to put it in question and answer format so you can simply scan down the questions and see which ones interest you. So, without further to do, let’s get started.

Are ISBNs reusable?

Once an ISBN has been assigned to a specific book, it cannot be reused.

What is the difference between a 10-digit and 13-digit ISBN?

As discussed in part 1 of this series, ISBNs came into existence in the early 1970s. At that time, they were all 10 digits and remained that way for over thirty years. On January 1, 2007 the ISBN system switched to a 13-digit format – presumably to provide additional numbers. Now all ISBNs are 13 digits long.

It’s worth noting that you can’t simply create a 13-digit ISBN from a 10-digit by merely adding “978” to the beginning. There is an algorithm that frequently results in a change of the last digit of the ISBN. Therefore, if you wish to convert from one to the other you need to use a conversion tool found HERE.

Where is an ISBN located?

There are usually 2 places an ISBN can be found. The first is usually on the copyright page, and will be listed as a 10-digit number, 13-digit number, or both and will look similar to this:

On printed books, you will also find it in the lower right corner of the back cover. It will be represented by a bar code so it is readable by scanners. Incidentally, I will cover bar codes in a future post.

Do I need separate ISBNs for a paperback and hard cover of the same book?

A paperback and hard cover of the same book would be considered different editions. Therefore, you would need a separate ISBN for each. This makes it very easy for anyone searching for a specific book to know whether they are looking at a paperback or hard cover just by the metadata.

If I revise my book, do I need a new ISBN?

The answer to this comes down to what changes were made. Correcting typographical or grammar errors is usually considered just a reprint of the same edition. These sorts of changes don’t require a new ISBN. However, doing a major revision or adding a substantial amount of new material would be considered a new edition. This would require a new ISBN. In general terms, if a book is revised by about 70% or more, it would be considered a substantial revision, and therefore, require a new ISBN.

If I change my book cover do I need a new ISBN?

This would not be considered a significant change since the text has not changed. As such, you can continue using the same ISBN.

Do different file formats (e.g. PDF, epub, etc.) require separate ISBNs?

Each different format of an electronic publication which are available separately should be given a separate ISBN.

Do I need different ISBNs for different versions of my ebook even if all versions have the same file format (e.g. PDF)?

The answer to this question has to do with the files themselves and the DRM (Digital Rights Management) software used to create and/or access them. Essentially, if the files have substantially the same content and settings and are equally operable on different devices or software, then a single ISBN can be used. Alternatively, if the same DRM software is used on two versions but with significantly different settings (e.g. one allows printing, but the other does not) then each version should have its own separate ISBN.

Also, separate ISBNs should be used when there is a standard and an “enhanced” version of an ebook having the same file format. Because the enhanced version includes audio, video, or other additional content not included in the standard version, it would be considered a different product.

In addition to the above, if a version is tied to a specific platform, device, or software by use of proprietary DRM, then separate ISBNs should be used for each such version. As an exception to this last statement, certain platforms (e.g. Amazon Kindle) don’t require ISBNs for digital files since they are the sole provider of ebooks in the proprietary format they support.

While certain platforms may not require separate ISBNs, they may be warranted for your own purposes, or if you want a particular version to be listed in third-party databases of available ebooks.

Well there you have it…my quick and easy guide for ISBN assignments. Should you find that your question didn’t get answered above or in Part 1 of this series, please feel free to contact me, and I will do my best to track down an answer for you.


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