What is MOBI? MOBI vs EPUB vs AZW – What Are the Differences Between eBook Readers Formats?

A few recent years back, eBooks were read by a very niche audience, people who thought buying and reading eBooks is a good to reduce deforestation and clutter around their homes and many people still think that. Then Amazon launched their Kindle devices, which were purposely made to read eBooks with a display that mimics the printed page of a book. If you want to move to reading books electronically and want to know the differences between eBook reader formats, here is a summary of what is MOBI, EPUB and AZW are and the differences between them.

These devices got popular very fast and Amazon became the pioneer of making a place for eBooks in an online store. Looking at Amazon, Barnes and Nobel, Apple and Google also launched their eBook stores for their own devices. The biggest advantage of eBooks is their ability to sync across multiple devices and storing complete books in the smallest size possible.

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Many people still think that reading the physical copies is much better and eBooks will reduce or even led to a stop of their production. People who are new to eBooks often ask what is the difference between the different eBook readers formats. This is a very common question which we want to answer in this article.


EPUB eBook Format

EPUB is the most popular, widely used and recognized eBook format. EPUB is short for electronic publication and it can be identified on your computer with the. epub format. EPUB is an open standard format for eBook publishing and was created by the International Digital Publishing Forum (IDPF). EPUB is supported by a large number of vendors and the. epub file supported by a large number of softwares and devices including Adobe Digital Editions, iBooks (iOS), Blackberry, Google Play Books (Android), Calibre (Windows) and many others. Currently, EPUB is only not supported by Amazon Kindle which uses the proprietary AZW format.


An EPUB file is basically a ZIP archive that contains HTML files, CSS style sheets, images, metadata and other assets.

What is MOBI eBook Format

What is MOBI? MOBI or also known as Mobipocket is an eBook standard format developed and launched by Mobipocket in France March, 2000. Amazon bought the company along with their standard in 2005. Many books available on Kindle are in .mobi format. MOBI, like EPUB, is also very a very common format and can be viewed in various devices and softwares like Calibre (Windows), Amazon Kindle (Android, Kindle, Windows, Mac), Mobipocket Reader Desktop and Aldiko Book Reader. MOBI is better suited for smaller screens due to its 64K image size limitation.

The MOBI format features:

● Reflowable content

● Advanced navigation controls.

● Indexing and high degree compression.

● Readers can add their own pages

● Readers can draw and add annotations.

● Page bookmarking and highlighting.

The MOBI format is an archive which uses XHTML and JavaScript along with support for HTML5 and CSS.

Many MOBI format vendors apply DRM on the MOBI eBooks for opening the eBooks on authorized devices or for authorized users.

AZW eBook Format

AZW or more commonly known as the Amazon Kindle eBook File, is developed by Amazon specifically for their Kindle eBook Readers. AZW is the proprietary format for Amazon’s Kindle store and Kindle eBook readers and it cannot be used by any other company or vendor. The AZW format evolves with every new tablet or eBook reader Amazon releases.

AZW format eBooks are Digital Right Management (DRM) restricted, which means that they are locked to the user ID or the device through which these eBooks were purchased. DRM free AZW eBooks are also available, but they are not different from the MOBI eBooks.


Now that we know what MOBI, EPUB and AZW are, we can easily analyze their differences:

MOBI, EPUB and AZW eBook formats all support DRM and all of these formats are available through different vendors on the internet but only the AZW eBook format is strictly supports DRM. MOBI and EPUB eBooks have optional DRM and are available or can be created DRM free.

EPUB is an open format, so it is available freely and also through vendors with DRM like Apple iTunes, Google Play Books, Barnes and Noble. MOBI and AZW formats are both of Amazon so they are available in Amazon’s Kindle store and are supported by Kindle eBook readers. AZW being Amazon’s proprietary format, is only available in the Kindle Store.

All three formats support reflowable content. But only in MOBI and AZW eBook formats, people can draw and add annotations on the eBooks. EPUB does not support these functions, but users can do this on different apps and softwares.

EPUB and MOBI eBook formats can be viewed almost on all major operating systems like Windows, Linux, Mac, Android and iOS. AZW is strictly accessible on Amazon’s Kindle Store and Kindle eBook readers and desktop eBook reader.

EPUB is an open standard format maintained by the International Digital Publishing Forum (IDPF), whereas the MOBI and AZW formats are proprietary formats and owned by Amazon.

MOBI was bought by Amazon and the AZW format is a modification of the MOBI format.

Final Wordings

Now you know what is MOBI and the differences between eBook reader formats, MOBI vs EPUB vs AZW. There is much confusion about these formats, but there are many tools available to convert these formats to another so that we can view them on different devices. We hope it was very useful for you to know the differences between MOBI, EPUB and AZW.