Hugh McGuire

Pressbooks helps you create high quality ebooks that meet the industry standards set by the International Digital Publishing Forum (IDPF) and submission requirements of all mainstream ebook retail platforms. Supported ebook formats on Pressbooks include EPUB 2. EPUB 3 files are also available in beta format.

Before you submit your ebook files for publication, we highly recommend testing your files on a few common ebook platforms. Read on for a list of recommended ebook testing tools.

Free Ebook Testing Tools

The ugly non-secret of ebooks is that they look different on just about every platform. No matter whether it’s Kindle or iBooks or Nook or Kobo or some other reading platform, you should expect some variation in the reading experience. Pressbooks works hard to standardize the design of your ebooks, but if you want to know exactly how your book will look after it’s available for purchase, we suggest downloading your ebook files and viewing them on a few of the free ebook reading tools listed below.

  1. Adobe Digital Editions
    ADE is Adobe’s free desktop EPUB reader. Since ADE was one of the first widely accepted ebook-reading technologies available, it’s used to power a lot of different services’ ebook platforms. How your book looks on ADE is a good indicator of how it will look elsewhere.
  2. Kindle Previewer
    Kindle Previewer is a free desktop application that enables authors, publishers and eBook service providers to preview how their books will appear when delivered to Kindle customers, and makes it easy to audit books for different screen sizes, display orientations and font sizes. NOTE: Amazon has discontinued support for the MOBI file format previously used for Kindle and now endorses the uses of EPUB for reflowable book formats on its platform. Accordingly, Pressbooks no longer supports MOBI exports.
  3. Apple Books
    Apple Books is an ebook reading application available on all iPhones by default. It can also be used to read ebooks on MacBook computers, on iPads, and on the iPod Touch. This software is free, but can only be downloaded if you have an Apple device.
  4. Rakuten Kobo 
    Kobo is another common ebook reader. You can download the Kobo application on your phone to view your EPUB files. It’s also possible to transfer your EPUB files directly from your desktop to your Kobo device.
  5. Dropbox
    Dropbox is a great tool to let you access files from multiple devices — drop your EPUB file into a folder in dropbox, and then you can access it from any device.
  6. IDPF Validator
    The International Digital Publishing Forum maintains a tool that allows you to “validate” your EPUB, or make sure that the file conforms to globally accepted standards and specifications required by all ebook platforms. EPUB files with validation errors may be rejected from ebook retailers, which is why we recommend either testing your files with IDPF or enabling Pressbooks error reports before you submit your files for publication. Read on for more details.

Ebook Validation Logs & Error Reports

There’s a difference between testing your ebooks for design and testing them for functionality. The majority of the tools listed above will help you test for design. You can use them to see what your ebook will look like on distributor platforms and get a pretty good idea of the reading experience your book will offer. When testing on Kindle Previewer, or Apple Books, or Adobe Digital Editions, you’ll want to keep an eye on things like fonts, colors, and margins.

Testing for functionality involves making sure that your book meets all the technical specifications required for submission to distribution services. That means that all the correct metadata has been included, that there aren’t issues with how your images have been embedded, and that all your internal links have been set up correctly.

By default, ebooks created on Pressbooks are built to conform to these specifications. However, the content that you import into Pressbooks may introduce validation errors that Pressbooks is unable to resolve automatically.

The last of the tools listed above, the IDPF Validator, does help you test your EPUB files for functionality. You can also receive error reports from Pressbooks automatically by following these steps:

  1. Go to Settings > Export from the left sidebar menu of your book’s dashboard
  2. Find the Email Validation Logs setting and change it from “No. Ignore validation errors” to “Yes. Email me validation error logs on export”
  3. Click Save Changes 

Pressbooks will then scan your files for validation errors every time you export a fresh set. If a validation error is found, the error will be flagged on the export screen, and a report will be sent to the email associated with your Pressbooks account. If you need help figuring out what the error report says, check out our Validation Logs chapter.


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Pressbooks User Guide by Hugh McGuire is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.

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