What is a MOBI file? A MOBI file is a digital book (eBook) saved in the proprietary MOBI format. It contains binary data that makes up an eBook (a book, magazine, scientific publication, etc.) and may incorporate DRM copyright protection to prevent copying or unauthorized viewing. Various eReaders, tablets, and software, including Calibre and Geometer Plus FBReader , support MOBI files.

More Information MOBI file open in Calibre 3 The Mobipocket Reader initially used the MOBI format, then other readers eventually supported it. The format supports various features including notes, corrections, and bookmarks. Amazon acquired MOBI in 2005 and used it exclusively for its eReaders. It then replaced MOBI with the Kindle Format 8 (KF8), which was saved and distributed as .mobi or .azw3 ( .AZW3 ) files. However, Amazon discontinued the development of the AZW3 and MOBI formats in 2022 in favor of the industry standard.EPUB format.