ePUB Explained: What You Need to Know About this Ebook Format

An e-reader and physical books.

Digital reading is big business, and with it comes a number of different formats. While PDF, MOBI, and more are all options, the ePUB format is a widely-supported open format for ebooks that is important to understand. In this post, we discuss the ePUB format in detail and show you show to open an ebook using the .epub extension.

What Is ePUB?

The “Electronic Publication” (ePUB) file format is an open method of creating an ebook. It’s been at the forefront of open standards for digital reading for more than a decade and is a vendor-independent standard for publishing digital books.

The format uses XHTML and CSS within the file to render pages, which means it’s a straightforward format for producing content. It combines with the Open Packing Format (OPF) to provide aspects such as a table of contents, metadata, and other ebook features.

Overall, it’s a flexible way to produce an ebook, and it holds a number of benefits over other formats.

Why Choose the ePUB Format Over Others?

When it comes to other ebook file formats, you’ll come up against MOBI, AZW, and PDF versions. This is a bit of a maze, because some of these are proprietary formats, and others aren’t a strict way of creating an ebook.

Here’s a quick list of benefits of ePUB over other formats:

  • It’s nearly guaranteed that you can read an ePUB format ebook on any device, except for Kindle. Amazon Kindle doesn’t support the format in any way, choosing to stick with its proprietary formats.
  • ePUB formats support colors, video, and more. This is in contrast to formats such as MOBI, which are more limited.
  • You’re not tied to a specific device with ePUB formats, as it’s an open standard. This gives you more choice of device and lets you steer clear of Amazon’s ecosystem if you wish.

These are all great benefits, but we have to restate that ePUB is open compared to almost all other ebook formats. This means it’s supported by more authors and publishers and will be available for almost every device.

Epub Explained E Reader

Here’s a quick rundown of the different file formats compared to ePUB:

ePUB vs. PDF

The difference between ePUB and PDF is with the contrasting flexibility of each format. PDF isn’t set up for the necessary adaptive elements of ebooks. In fact, the format and layout of a PDF will be consistent regardless of where it’s viewed.

The positives of a PDF over an ePUB are that they can be more interactive and contain a wide range of media (such as audio and video) as a result. On the whole, though, an ePUB is much more suitable for ebooks, as it’s much smaller in file size and versatile with regard to the interactivity it offers a reader.


The first advantage for ePUB over MOBI is greater potential reach with regard to marketplaces. An ePUB format is compatible with all major ebook retailers.

In contrast, MOBI formats only cover two retailers: Amazon and Kobo. Of course, it could be that while you’re happy with this coverage, you’re missing out on Google Play, Apple Books, and the Barnes & Noble Store. In fact, an ePUB is the only format accepted there of those we mentioned.

Because it’s a proprietary format, you’ll find that few sites cater to MOBI files. Given that Amazon uses AZW files now at a greater frequency, it could be that MOBI will gather dust on the virtual shelves. When it comes to features and functionality, though, MOBI (and AZW) are just as capable as ePUB.

How to Read an ePUB Ebook

The great news is that you can read ePUB books in most apps and tools. For example, you can import them to Kobo and Nook devices.

Though, there are many other apps that cut the mustard, Apple device users can import into Apple Books and get a solid experience:

The Apple Books marketplace.

Android users can opt for a number of ePUB readers, such as Moon+, Lithium, and many more.

Desktop users will do well to download Adobe Digital Editions.

The Adobe Digital Editions app.

This is a free ebook reader that supports the ePUB format. If you purchase an ebook, many stores ask you to verify the Digital Rights Management (DRM) through this app.

Reading an ebook with this app is as simple as right-clicking and selecting “Read” from the context menu.

Choosing a read a book in the Adobe Digital Editions app.

This will open the ebook in a native app reader.

The Adobe Digital Editions reader.

You’re even able to read ePUB files in the browser. EPUBReader for Firefox is a fantastic add-on for the task. Simple EPUB Reader for Chrome is another good solution for that browser. The Google Play store also lets you read ePUB format ebooks, which can do in a pinch (although we’d recommend a dedicated app).

How to Convert an Ebook to the ePUB Format

There is one app that we’ve left off the list because it’s more of a digital ebook library manager than a pure reader. Calibre is an open-source solution to manage your digital library and is a cross-platform app, too.

This offers a flexible system for importing your ebooks and also converting them from one format to another. In this author’s constant use of the app, there has been no perceptible quality issues from the conversion process.

What’s more, you can store multiple versions of your ebook under one entry. This means you can convert a PDF to an ePUB, MOBI, and more without viewing duplicates within your library list. Follow the instructions below:

  1. Open Calibre and right-click on the ebook you’d like to convert.
The Calibre right-click context menu.
  1. Click “Convert Books -> Convert Individually” (or one of the other options if you have more than one book in mind. This will bring up a dialog screen for the book.
  2. Here, you’ll want to choose “EPUB” from the “Output format” drop-down menu.

Bear in mind that this conversion process gives you flexibility in that you can convert a PDF to an ePUB or a MOBI and vice versa.

Selecting an output format in Calibre.
  1. Once you click OK, Calibre will start a “job” for converting the book.
A Calibre job running.
  1. When finished, you can select the book and its versions from your library list.
Choosing a book in Calibre.

It’s a quick and easy process – means when it comes to digital book management, Calibre is one of the best.

Frequently Asked Questions

Can I convert other book types with a Digital Rights Management (DRM) restriction to ePUB format?

You can convert DRM-protected ebooks to ePUB with Calibre. However, note that the conversion process won’t remove the DRM. You’ll still need to use the Adobe Digital Editions app if you want to read your ePUB ebook with DRM.

What is the availability of ePUB ebooks on digital book stores, such as Amazon, ebooks.com, and others?

As we noted, ePUB formats adorn the virtual shelves of most digital booksellers. However, stores with their own proprietary format, such as Amazon and Kobo, won’t stock ePUB formats for obvious reasons.

Where can I find free ebooks in the ePUB format?

Because the ePUB standard is open, this means you can also find free ePUB ebooks all over the Web.

For example, epubBooks is a popular site. Project Gutenberg also curates thousands of free books from the public domain.

Our advice is to search the Web and find a couple of sites you like the look of. However, we should state that we’re not condoning theft of copyrighted and “cracked” ebooks. You should pay for ebooks where necessary. We like the deals you will often see over at Humble Bundle on technical and educational books, all in the ePUB format.

There are many benefits to reading ebooks, but DRM is still prevalent. What’s more, Amazon is the largest online retailer for ebooks, yet it doesn’t support ePUB in any capacity. If you want to buy your ebooks from another retailer, you’ll want to get to know the ePUB format – and use it often.

Your PDF files are a great fit for the ePUB format, so you may want to convert them. Read on to learn of more apps to help you read ebooks.

Tom Rankin
Tom Rankin

Tom Rankin is a quality content writer for WordPress, tech, and small businesses. When he's not putting fingers to keyboard, he can be found taking photographs, writing music, playing computer games, and talking in the third-person.

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