For over a decade, self-publishing authors who were looking to distribute their ebooks with major retailers had two different ebook formats to manage: EPUB files and mobi files. But with recent developments on KDP, Amazon’s author publishing platform, most indie authors now only have to deal with one format: the EPUB.

In this post, you’ll learn about the most popular ebook formats of 2021, and discover the one reason why the mobi format isn’t completely dead and gone.

What is an EPUB?

Sample EPUB Files Download. Electronic Publication File Format. Is a popular file format used for storing eBooks. It can be opened with most eBook readers though you will have to convert them into Amazon’s proprietary eBook format for use on Kindle devices. Most ebook reading devices use the epub format. But the mobi ebook format, or Kindle book format, is the only file type that can be read on Kindle devices and Kindle apps. Converting is the only way that you can check and make sure that you correctly formatted your Microsoft Word document for ebook reading. The EPUB format is an open standard. That means it is free and publicly available though there are specific rules for its usage. The EPUB standard is maintained by the International Digital. EPUB is an e-book file format that uses the '.epub' file extension.The term is short for electronic publication and is sometimes styled ePub.EPUB is supported by many e-readers, and compatible software is available for most smartphones, tablets, and computers. Certified by the International Digital Publishing Forum (IDPF), EPUB is the most widely supported vendor-independent eBook format. Simply put, it can be read by more eBook readers than any other format in the world. EPUB files also carry with them a huge number of benefits.

An EPUB file is the most widely accepted ebook format on the market. It’s the industry standard, used by Apple, Kobo, Barnes & Noble, Sony, and Google e-readers. A free and open standard based on HTML (much like the files your web browser would read), EPUB is a flexible format that supports a wealth of features. It can:

optimize a book’s text to fit your device;
embed images;
allow for bookmarking, highlighting, and text-to-speak.

The latest version, EPUB 3, will even permit you to add multimedia content like video and audio clips.

All things considered, it’s a pretty great format — which is why the publishing industry has rallied around it as its ebook format of choice.

What is a mobi file?

Mobi files are the ebook files used exclusively by Amazon’s Kindle devices. Or, if we're staying up-to-date, the actual proprietary standard is now called AZW (or AZW3 or KFX depending on the generation). Without getting into the weeds with technical details, the major difference between mobi files and EPUBs is that the Amazon format is protected by Digital Rights Management (DRM) which ‘locks’ the book so it can only be read on devices associated with your account.

Amazon is the largest ebook retailer in the world by quite a long way: in 2015, they were responsible for over 70% of ebooks sold in the US. This massive market share was part of why they could insist on using their own format for such a long time.

However, as of 2020, authors are now encouraged to upload EPUB files of books they’re looking to publish. In fact, uploading a mobi version to Kindle Direct Publishing (KDP) isn’t even an option anymore.

Top Tip: To make sure that your book looks just right before you start selling it on Amazon, you can upload and validate your EPUB using Amazon's own Kindle Previewer tool.

Is the mobi format now dead?

The format hasn’t joined the choir invisible just yet: all Kindle devices still use mobi files for ebooks. When authors and publishers upload their EPUBs to KDP, the platform quietly converts them into the mobi format, which they will sell through their online stores.

The only reason anyone still might have to create a mobi file themselves is to “sideload” a book onto a Kindle device.

What is sideloading?

Sideloading is where you download a book that you haven’t purchased from a store onto an e-reader. The most common (legal) reason to sideload a book is to read an ARC (Advanced Reader Copy). So if you wish to share an early version of your ebook with a reviewer who owns a Kindle e-reader, you’ll need to send them a mobi version.

Free course: Self-Publishing 101

Join the self-publishing revolution and become an indie bestseller with this 10-day online course. Get started now.

What's the easiest way to convert EPUB to mobi?

If you have an EPUB that you want to convert to mobi right now, you can simply put it through our EPUB to mobi converter! You'll get a beautiful new mobi file in your email inbox within minutes.

Note: our EPUB to mobi converter also offers instructions for sideloading books onto a Kindle.

Format Epub To Mobi

When should you use PDF files?

The PDF, which has remained one of the most popular document formats since its debut in 2001, is still widely used in publishing for two purposes.

Print on Demand

Perhaps the most cost-effective way of selling physical copies on a small scale, self-publishing authors commonly use what’s called a print-on-demand (POD) service. Instead of ordering a print run and filling a warehouse with paperbacks, copies will only be printed as and when they’ve been purchased either by individual buyers or a bookstore.

The two most popular POD services are IngramSpark and KDP Print (formerly CreateSpace), the latter of which is — would you believe it? — an Amazon company.

Epub Format Specification

For this, you will need a file that contains strict definitions of your book’s layout and content – which is why we use PDF files. There are countless different types of PDF out there but for our purposes, the format will need to a ‘print-ready PDF’ to make it compatible with printers. Any hyperlinks will be removed and your image colors will be expressed in CMYK, and not using the RGB color model.

Graphically Intensive eBooks

Both EPUBs and mobis are great at handling text-intensive books like novels, memoirs and some non-fiction books. They are, however, less awesome at dealing with books that have a lot of images, graphs and photos — art books and travel guides, for example. If you need your ebook to look exactly the same as the print version, you may wish to sell it as a PDF, which will ensure fidelity across all devices.

The downside is that basic black-and-white Kindles (and e-readers like it) will struggle to display them well — as these PDF books will tend to be fixed-width. Rosen frederiksberg slot. Unlike an EPUB file, where the text is 'reflowable' and will adapt to the shape and size of your device, reading a small-print PDF book on a Kindle Paperwhite is nothing short of a chore.

Creating EPUBs and print-ready PDFs

Reedsy offers a free online book editing tool that lets you professionally format a book with no training required. Once you’re happy with how it looks, you can export your book for free as both EPUB and print-ready PDF files!

To find out more about how the Reedsy Book Editor can help you publish your own book, click here.

To learn more about how to set up your ebook on the different retailers, read our master guide on ebook publishing platforms.

[updated: 11/03/2020 UTC]

We’ll take a closer look at the EPUB and Kindle ebook formats which are responsible for most of the ebook market’s growth over the past few years. We’ll also examine the new versions of these formats which are likely to drive the direction of the ebook market over the next few years.

The two formats that matter most today

We start with a look at the two ebook formats that matter most today: Kindle and EPUB. These formats adhere to the features we’ve seen that have made ebooks successful.

They work well in both dedicated e-readers and in devices such as tablets, or even smartphones. And they enjoy large, global distribution channels.

New versions — EPUB3 and Kindle KF8 — take advantage of more powerful e-readers and move ebooks beyond their mostly-text stronghold. But they’re slow to catch on and the older ebook formats still dominate.

We’ll lo