File type with .mobi extension is format, which can be used to create files especially for MobiPocket Reader. It is adapted for e-books, but incorporation Amazon has different label for this file format, so called AZW. This company uses this file type for files created by KindleGen, but it has several disadvantages. First is that it uses the wrong text wraping, there are different sizes of tables across devices. Hovewer it has some advantages, like support of HTML and CSS.
Originally was this format derived from PalmDOC with some changes, especially by using HTML. That causes great compression abilities. In fact there are not many programs which can open files saved using this file format. That is due to its great compression. One of these programs is Calibre, which is available for all great operation systems – Windows, Mac OS and Linux.