What Is a MOBI File?

This article describes what MOBI files are, how to open one, and how to convert one to a different document format so that it works on your device.

What Is a MOBI File?

A MOBI file is a Mobipocket eBook file. They're used for storing digital books and are designed specifically for mobile devices with low bandwidth.

MOBI files support things like bookmarking, JavaScript, frames, and adding notes and corrections.

How to Open a MOBI File

Some free programs that can open MOBI files include Librum, Calibre, Stanza, Sumatra PDF, Mobi File Reader, FBReader, Okular, and Mobipocket Reader.

MOBI files can also be read by popular eBook readers like the Amazon Kindle and many smartphones that support the format.

Additionally, many eBook readers—again, like the popular Kindle device—also have desktop software, mobile apps, and browser tools that allow the reading of MOBI files. The Amazon Kindle App is one example that supports Windows, macOS, and mobile devices; and Kindle Cloud Reader can be used to read MOBI files online, although you can't use them with the Send to Kindle app.

How to Convert a MOBI File

The quickest way to convert a MOBI file is to use an online converter like DocsPal. You can upload the MOBI file to that website or enter the URL to an online MOBI file, and then choose one of many different file formats to convert it to. EPUB, LIT, LRF, PDB, PDF, FB2, RB, and several others are supported.

If you already have a program on your computer that opens MOBI files, you may be able to use it to save the MOBI file to one of a different format. Calibre, for example, can convert MOBI files to lots of different formats, and Mobi File Reader supports saving an open MOBI file to TXT or HTML.

MOBI files can be converted with other Free File Conversion Software Programs or Online Services, too. An excellent example is Zamzar, an online MOBI converter. It can convert MOBI files to PRC, OEB, AZW3, and many other popular file formats, and all you have to do is upload the MOBI file to Zamzar and then download the converted file—nothing needs to be installed on your computer.

More Information on MOBI Files

Mobipocket has been owned by Amazon since 2005. Support for the MOBI format has been discontinued since 2011. Amazon's Kindle devices use the MOBI structure but the files have a different DRM scheme and use the AZW file extension.

Some Mobipocket eBook files have the .PRC file extension instead of .MOBI.

You can download free MOBI books from a variety of websites, including Project Gutenberg, Feedbooks, and Open Library.

If other things are added to a MOBI file, such as bookmarks or annotations, Kindle applications store them in a separate file that uses the .MBP file extension. If the file is encrypted, it uses the .SMBP suffix instead.

You can make a MOBI file using Amazon's free KindleGen command line tool.

MobileRead Wiki has lots of information on MOBI files if you're interested in a deeper read.

Still Can't Open the File?

If you can't open your MOBI file with the suggestions from above, double-check that you are in fact working with a file that has the .MOBI extension. This needs to be understood because some files look like MOBI files but really aren't related at all, and so they most likely can't be opened with the same software.

MOB (MOBTV Video) files are one example. Even though they might be confused with MOBI files, these are video files that can only be used with multimedia applications like Windows Media Player. If you tried opening a MOB file with an eBook reader, you'd either get errors or be shown a bunch of incoherent text.

MOI Video files (.MOI) are similar in that they're related to video content, but they, too, cannot be opened with any of the text-based file readers or converters mentioned above.

Re-read the file extension and then do a search here on Lifewire or on Google to learn more about the format and to find out which programs are able to open or convert it.