Most writers, deep in their first drafts, are not wondering about ebook file formats. But at some point, particularly if you’re self-publishing, the practical question of how your book reaches your reader’s device, will need to be answered.
The epub vs. mobi question is one that comes up in self-publishing conversations, and it actually creates more confusion than it deserves. The short answer is that the self-publishing landscape shifted considerably in recent years, and what was once a genuine choice you had to consider has largely resolved itself. Understanding why can help you make better decisions about your own publishing workflow.
In this article, I’ll explain what epub and mobi file types are, discuss the situations where each format is appropriate, and the major differences between them. Lastly, I will provide you with a Story Weapon that will eliminate the need to make any guesses on the decision.
Epub vs. mobi used to be a real decision for self-publishing authors, but epub has become the clear standard since Amazon dropped mobi support for KDP uploads in 2022. Epub is an open format accepted by nearly every platform — Apple Books, Kobo, Nook, Google Play — while mobi now matters only for older Kindle devices or direct sideloading. For most writers, defaulting to epub and moving on is the simplest path forward.
Understanding epub and mobi file formats
To get a good idea of epub vs. mobi, it helps to get under the hood and understand what they’re doing.
Epub stands for “electronic publication.” It’s an open standard. This just means it isn’t developed by a single company, and therefore, is not owned by anybody either. The International Digital Publishing Forum keeps up the epub format. It is optimized for a variety of devices and reading applications. Open and widely accepted, epub is the ebook world’s closest approximation to a universal format.
Mobi was originally developed by a French company called Mobipocket and subsequently bought by Amazon. For years, mobi was Amazon’s ebook format for Kindle devices in the Kindle app. That was simply what the Kindle ecosystem ran on.
Both formats have a similar operation. They compress your text, pictures, and formatting into a file that can be displayed by a reading device. They both use reflowable text. This is the great thing that allows readers to change the font size, screen brightness and text spacing on their device without breaking the layout. This is a vital ebook function that works in epub and mobi.
The distinction is not really over how they deal with your content. It’s in who built them, who uses them, and which platforms accept them.
Where each format lives and works
When you understand the natural habitat for each format, the answer to epub vs. mobi is much less complex.
Epub is accepted almost everywhere in online publishing platforms. Apple Books runs on epub. Kobo runs on epub. Barnes and Noble’s Nook platform uses epub. Google Play Books accepts epub. The epub format is the default format for Smashwords (or Draft2Digital), and most other ebook distributors. For publishing across a number of platforms, epub is the format you’ll need.
Mobi was historically the format for Amazon and Kindle. If a writer wanted their book on a Kindle device in the early years of ebook publishing, they needed a mobi file. This made mobi a standard part of the self-publishing conversation for a long time. Amazon was simply that dominant in the ebook market.
But then things changed. Amazon announced in 2022 that they would be removing support for mobi files for the Kindle Direct Publishing upload process. Amazon now favours epub for new uploads.
Amazon also has its own newer ebook format called KFX, which gets generated automatically when they process your epub file. This was a significant change. It effectively made mobi much less relevant for most writers going through a standard publishing workflow today.
Mobi files still work on older Kindle devices. They can also be sent directly to a Kindle via email. The format hasn’t disappeared entirely, yet. But for most writers starting the epub vs. mobi conversation fresh today, be aware that epub has become the standard.
What’s the difference between epub vs mobi?
File size tends to differ slightly. Mobi files are often larger than epub files while containing the same content. This rarely matters for most books, but it’s worth keeping in mind for authors with material heavy in images or illustrated content.
Formatting complexity is also an area where epub tends to have an edge. Epub uses open Web standards, such as HTML and CSS. This generally makes it easier to apply more sophisticated formatting. Users creating ebooks that consist of lots of images or are designed with multiple layouts prefer epub for added flexibility.
Compatibility is perhaps the most practical difference. Epub opens in more places out of the box. If someone downloads an epub, they can read it on Apple Books, Adobe Digital Editions, Google Play Books, Kobo, and dozens of other applications relatively freely. A mobi file was locked in the Kindle ecosystem. To maintain their competitive edge in the self-publishing market and keep writers coming to their platform, Amazon traded exclusivity for ease-of-use and switched over to epub.
For anyone publishing widely today, epub is the format almost all distributors accept. If you have a well-formatted, clean epub, you will have the greatest flexibility with the least additional work converting it.
Your story weapon: Default to epub and move on
Self-publishing might feel overwhelming when you encounter it for the first time. You have to research different platforms available to you, what formats they require for your manuscript, metadata to fill in, and cover specifications to meet all before a single reader has a chance to find your book. It is easy to get lost in the logistics and lose sight of the fact that these steps exist to serve you as the writer, not the other way around.
Thankfully, the epub vs. mobi question is one you can resolve simply. Default to epub! Use that file as your primary upload across ebook publishing platforms. It is the format that travels furthest with the least friction.
Some readers may request a mobi file if you will be offering your book directly to your readers via a personal author website. They may be using an older Kindle and want to sideload their books. When that’s the case, it can be helpful to have a mobi version ready, but it’s not required.
What matters is that the book exists, that it is formatted cleanly, and that it can reach the reader in a form they can actually open and read without difficulty. Everything beyond that is administration. Do the administration efficiently, put it behind you, and get back to writing. That is where your attention belongs.
Understanding the technical side of publishing helps remove unnecessary obstacles, allowing you to focus your time and energy where it matters most: writing exceptional stories. Whether you’re preparing your first manuscript for publication or refining your long-term publishing strategy, developing a solid foundation in both craft and process will serve you throughout your career. Take the next step and join one of my next workshops: The 90-Day Novel, The 90-Day Memoir, Story Day.
