Mobipocket

The Mobipocket software package was free and consisted of various publishing and reading tools for PDAs, smartphones, mobile phones, the e-readers Kindle and iLiad, and applications on devices using Symbian, Windows, Palm OS, Java ME and Psion.

By using third-party programs such as Lexcycle Stanza, calibre or Okular, unencrypted Mobipocket books could also be read on Mac OS X, iOS, Android devices and Linux.

[6] A user could thus create documents in the Mobipocket format .mobi[7] and use personal comments, bookmarks, and more on all devices supporting those features.

Additionally, Amazon offered a free program called KindleGen that could convert or create documents in the Mobipocket format.

[10] User-added information, such as annotations and bookmarks, were kept in separate ".mbp" files by the official Mobipocket Reader and Kindle applications.

Mobipocket on a Psion Series 5 PDA (with further information)