EPUB vs MOBI: Which Format is Better for Publishing Your Book?

Lorraine Claire S. Rafols
April 03, 2020 | 10 mins
EDITOR'S NOTE: As of August 1, 2021, Amazon will no longer support MOBI files for re-flowable ebooks. You can find more information on Amazon's help center article. Thus, the debate is over: EPUB is the winner! 

EPUB vs MOBI is a debate that has been going on for years among book authors, publishers, marketers, and other self-publishing enthusiasts. 

And why the squabble over two “innocent” eBook formats? 

Thanks to advances in technology – the WWW, smartphones and tablets, reader software and a host of digital publishing platforms – EPUB and MOBI have risen to become the top two most popular eBook formats circulating by the millions today. 

If you’re serious about becoming an author and learning how to write a book to self-publish on Amazon… read on and learn about these two eBook formats. 

Related: How to Publish an eBook

Need A Nonfiction Book Outline?

Here’s what we’ll cover in this guide: 

  1. History of EPUB and MOBI
  2. What is the EPUB format? 
  3. What is the MOBI format? 
  4. EPUB vs MOBI: Pros & Cons
  5. Final Verdict: Which Should You Choose?

A Brief History of EPUB and MOBI

The EPUB format came into the picture on September 11, 1999, when David Ornstein brought out an eBook with a new specification, OEB (Open EBook). This HTML-based format is EPUB’s earliest precursor and was developed by the Open eBook Forum, later known as the International Digital Publishing Forum (IDPF).

It was not too long when Mobipocket SA released the PRC format in 2000, changing the world of digital publishing forever. This revolutionary eBook file featured reflowable text that adjusts to different screen sizes. 

PRC files were initially used in Mobipocket Reader applications for Palm Personal Digital Assistants (PDAs), Windows Mobile, Kindle, and Blackberry gadgets. 

When Amazon acquired Mobipocket SA in 2005, it ended support for all PRC files, causing them to become virtually unreadable on every other reading software – except Amazon’s own Kindle. PRC was then relaunched as MOBI, and subsequently, as AZW from 2011 onwards.

Here’s the twist…

Mobipocket SA created and shared free tools so that eBook publishers can utilize PRC files as binary wrappers for textual content based on OEB-standard HTML files. 

The tools came with user guides but without complete documentation of the specifications for both PRC and MOBI. 

(Wise move! Nevertheless, kudos to Amazon and Mobipocket for still being kind enough to share the code.) 

Since then, both EPUB and MOBI have applied the same text-wrapping features, making them the best eBook formats of choice at present.

So what’s the difference? 

What is the EPUB Format?

EPUB stands for Electronic Publication, an open standard, HTML and CSS-based format for eBooks created and supported by the International Digital Publishing Forum (IDPF), previously known as the Open eBook Forum.

EPUB has become, by far, the most widely accepted format for eBooks. 

Being industry standard, it is compatible with almost all eReader devices and applications, including major team players like Apple iBooks, Adobe Digital Editions, Aldiko for Android, Barnes & Noble’s Nook, Google Play, Kobo, and Sony eReaders.

What is the MOBI Format?

MOBI, short for Mobipocket, its original developer, is Amazon’s exclusive eBook format for all its Kindle readers. 

Related: Amazon KDP Guide

MOBI files are DRM-protected, which means that under Digital Rights Management, an eBook file is locked and can only be read on Kindle devices logged on to the associated Amazon account that purchased the book. 

MOBI files are based on the Open eBook XHTML standard, and later versions such as AZW have Javascript capabilities. 

A Comparison of EPUB vs MOBI: What are their Pros and Cons?

Knowing about these two formats, it’s no wonder that authors preparing to publish their masterpieces become torn.

Both EPUB and MOBI have unique advantages and disadvantages, so we summarized them for you into a list of seven factors to help you decide.

#1 – Both EPUB and MOBI have automatic reflowable text. 

Having automatic reflowable text is perhaps the single most important, non-negotiable feature that any eBook must possess. And thankfully, it has been successfully integrated into both EPUB and MOBI books. 

Reflowable text automatically adjusts to or “wraps” around the screen size of just about any reading device, allowing eBook fans to read comfortably. This feature has earned both EPUB and MOBI their reputation as the most trusted eBook formats. 

But the reflowable text, nearly perfect as it is for eBooks, also has limitations. 

Columns, Tables, and Illustrations

Cookbooks, design books, academic textbooks, coffee table books, and the like may encounter serious display problems if produced as either EPUB or MOBI. 

With their complicated layouts, these books might be less of a pain to read on fixed-width formats such as PDFs and devices with larger screens. 

If you have decided to publish your book as an EPUB or MOBI but feel that it will never be complete without a few tables and illustrations, you may add these elements in between paragraphs to prevent unsightly text reflow in the wrong places.

Typefaces or Fonts

Authors and publishers generally have no control over their eBook’s final font display. This usually depends on the reader who gets to pick from the font options provided by his or her reading app. 

Changing an eBook’s default font may severely affect its pages’ overall appearance since its text may not wrap neatly. 

If you want a uniform typeface for all your eBooks, there is a way. You can always embed your font of choice into the book’s coding – easier to do on EPUBs which are HTML-based. 

Embedding fonts guides eReader apps into displaying text correctly – and not converting it into weird symbols – as well as preserving the sanity of your layout. 

Embedding is a useful technique for displaying fancy and non-Latin types, which are not recognized on most reading apps. (Although I definitely hope you won’t use these fancy fonts for your entire text, but only for chapter or part titles.)

If you don’t want the extra hassle of embedding, go for standard serifs like Times New Roman, Garamond, Century, or Bookman.


The actual pages of EPUB and MOBI books may vary on different screen sizes due to their reflowable text. Hence, footnotes may also move around and not stay on their designated page. 

There is hope for you and your eBook though. 

You might consider producing a PDF copy of your work to keep footnotes intact, or you may also convert your footnotes into endnotes, which work just fine on EPUBs and MOBIs.

#2 – EPUBs accommodate graphics and multimedia better.

Since EPUB files are based on HTML, they can be modified to include elements like images, audio, video and hypertext. All it will take is a bit of code-tweaking…and voila! Your plain-text eBook has morphed into a multimedia eBook. 

Who wouldn’t love some color and action in their eBook? When you’re writing non-fiction to teach or inspire, you might be thinking of supplementary media like tutorials or documentaries. These can be embedded in your EPUB file. 

There are three possible downsides to this feature:

  1. Large File Size. With each additional media, your EPUB’s file size will increase. I would recommend not to overdo it, or else your readers might have problems uploading, downloading or transporting your eBook. Worse, they might give up buying it altogether, which leads us to the next disadvantage…
  2. More Expensive. Supplementary material places a higher value and an above-market price for your eBook. Again, this may lead to your audience’s disfavor, since any buyer would go for the most cost-effective purchase. After all, people buy books to read and gain information, not be entertained by the attached multimedia.
  3. Bad HTML Layout. Failing to test the final output for your EPUB can pull down your sales even more. With EPUB’s automatic reflowable text, it is very crucial to check the placement of all text and multimedia embedded in your book.

#3 – MOBIs are usually plain-text and have a lower file size.

If you do not intend to add heavy graphics to your book, the MOBI format might be the better option for you. 

MOBI developers have limited the size and quality of images in a MOBI and placed a premium on its textual content. Thus, MOBI files come in lighter file sizes compared to EPUBs. They have been designed to be read even on low-end reading devices like the earliest versions of Kindle. For this reason, MOBI books are a welcome addition to any electronic bookshelf – on a budget! 

Due to lack of support and tools available, the older MOBI format is less flexible than an EPUB. Fortunately, Amazon remedied this by upgrading MOBI into AZW, which are very much like EPUBs that they can readily be converted into one. Perhaps, the only marked difference about AZWs is their even stricter DRM protection.

#4 – EPUB is vendor-independent. 

Being readable on the majority of eBook readers may well be the EPUB format’s greatest strength. 

EPUB is quite similar to PDF in that both are reputable industry standards – EPUB for eBooks and PDF for any fixed-width, printable document. Both can be read on virtually any device, be it smartphone, tablet, MAC or PC, as long as the appropriate reading software is installed. In addition, both can be shared with or copied to other devices, hassle-free. 

If you want to reach a wide audience, promote yourself or raise awareness, EPUB (and PDF) is the best option!

Moreover, if your authorial rights bother you, the EPUB format may not be for you (more about this in #6). Take note as well, that, although EPUB titles can be accessed on almost all readers, they cannot be accepted on Kindle, will not be sold on the Amazon bookstore, and will never be placed on the highly coveted Amazon charts.

#5 – MOBI is Amazon-exclusive.

We have mentioned previously that Amazon already has its own format, MOBI, which is readable only on Amazon’s reading device, Kindle. All eBook titles sold on Amazon are required to be in the MOBI or AZW format – knocking EPUB out of the game. 

Related: Amazon Author Central

Any author or publisher seeking to market books will likely publish on Amazon, which is considered to be the largest eBook seller in the world with millions of subscribers.

Amazon virtually rules the eBook market. Its paperback and hardbound titles nearly always have a lower-priced Kindle counterpart – in the MOBI/AZW format, of course!    

Related: Why BookBub is Amazon's Biggest Competition

#6 – EPUB is free and open-access.

EPUB is an open-standard format, which means that its eBooks are freely available to the public and are readily shared over the Internet or to any device.

This feature is quite helpful for noble causes such as spreading educational and well-curated information in contrast to the unevaluated information retrieved from a Google search. However, being free and open-access makes EPUB files more susceptible to piracy and plagiarism. 

#7 – MOBI is safe and DRM-locked. 

Authors desiring to protect their rights can breathe and sleep better if they publish their eBooks as MOBI files.

MOBI/AZW books are secure under Digital Rights Management (DRM). Granted you and your readers update your Amazon password regularly, your published MOBIs can never be stolen or leaked by third-party, unauthorized accounts, preserving your hard-earned royalties.

With DRM protection, copyright infringement on eBooks can be minimized and even stopped, so authors can receive the profits they rightfully deserve.

EPUB vs MOBI: The Verdict

Choosing the most appropriate format for your eBook boils down to your book’s intended purpose, your target audience, what device they will probably use to read it, and on which publishing platform you plan to launch or sell your book.

Related: Best Self-Publishing Companies

It is crucial to make the right decision here, as the wrong move may make or break your book’s success.

Here’s how to determine whether you should use EPUB vs MOBI:

#1 – Intended Purpose

Will your book be a freebie, a digital download, or a bait for generating leads to your business? Do you desire to freely share your knowledge and experiences to the public – with or without monetary gain? Then, you might consider publishing your book as an EPUB or PDF. 

Do you want to successfully market your book? Are you aiming to be the #1 bestseller in your category and earn a steady income from your book? By all means, pick MOBI or AZW, then launch your new book on Amazon

#2- Target Audience

What device is your target audience going to most likely read your book on?

If your book is written for people from different walks of life, select EPUB, which is generally accessible on most devices. 

But if your book is written for certain professionals, online shoppers, citizens of a particular country, or other specialized groups, MOBI could be your best choice – that is, if you believe the majority of your audience owns a Kindle.    

#3 – Publishing Marketplace or Platform 

Where on the World Wide Web do you plan to launch, promote and sell your eBook?

Related: Book Marketing

If itss Amazon, I’m positive that by now you know the suitable format to use. If it’s any other marketplace like Google Play or Apple, you already know the drill.

So, EPUB vs MOBI? 

If they still baffle you at this point, why not publish your book in these two formats (including PDF, if you’d like)? 

This way, you’re gonna have the most important backup file formats in your hands – and reach any audience or marketplace that you desire, the world over.

Read This Next
More Publishing, Reviews Posts

Join the Community

Join 100,000 other aspiring authors who receive weekly emails from us to help them reach their author dreams. Get the latest product updates, company news, and special offers delivered right to your inbox.