This article will go in-depth regarding the MOBI format, including what MOBI is, who uses it, and how to open and convert it.

What is MOBI Format and What Uses a MOBI File?

MOBI is an e-book file format used to store digital books and was created specifically for low-bandwidth mobile devices. It was first designed by MobiPocket Reader, and later purchased by Amazon to use on the Kindle devices. Amazon bought it in 2005 as a private format for eBooks on Kindle until it was discontinued in 2011.

MOBI files mainly come in two ways: one is from the conversion of EPUB, PDF, and TXT; the other is from Amazon stores.

Most e-books and libraries use EPUB (also an e-book file format) as a standard file format for e-books, while Kindle used MOBI for a long time. The current main Kindle formats, AZW3, KF8, and KFX, are almost based on MOBI. Why is Amazon so obsessed with MOBI?

According to USA Today's interview with Jeff Bezos (CEO of Amazon Group), he pointed out that Amazon innovates quickly, and the adoption of a standard format allows them to incorporate innovations into their products quickly.

However, there must be reasons why the mainstream uses the EPUB format, so what’s the difference between EPUB vs MOBI?


The main difference between EPUB and MOBI is that MOBI is mainly used on Kindle, while EPUB is supported across all platforms. The following chart tells you the specific platforms that EPUB and MOBI support, respectively:

Platforms EPUB MOBI
Apple Books ×
Google Play Books ×
Barnes & Noble Press ×

How to Open a MOBI File

MOBI files cannot be opened and viewed directly unless there’s a dedicated reader for this format. To read or view MOBI files, you need to download eReader programs on your device in advance.

There are many free MOBI readers on the market. If you prefer desktop software, you can try SumatraPDF, Calibre, Mobipocket Reader, etc. Besides, you can also convert MOBI files to other file formats. By this means, you are also able to read MOBI files on any device.

Take Calibre as an example. After downloading and installing this tool on your device, click Add books on the main menu to open MOBI files.

Of course, Kindle can also read MOBI files now, but you need to send the files to your Kindle first.

How to Convert a MOBI File

The image size in MOBI files cannot be scaled randomly, which makes it inconvenient to read the files sometimes. However, if you convert the MOBI files to other easy-to-read file formats, you will gain a better reading experience.

Calibre also supports converting MOBI files to other file formats and vice versa. If there’s a MOBI file on your PC and you want to check it on your phone, you can use Calibre to convert the file first, then send the converted file to your mobile device.

Of course, there are also many online converters to help you complete the conversion, such as Convertio, Zamzar, ConvertFiles, and so on.

Monica has accumulated more than three years of experience in writing tech products. Now she works as an English columnist for this website. With her extensive experience, Monica has offered many helpful and feasible recommendations.