is a format used in the MobiPocket Reader software on desktop and mobile platforms. Books in this format can have .prc and .mobi file extensions. MOBI was originally based on the PalmDOC format; adding HTML tags made it possible to create a high-compression version which compresses data to a high degree. There are a number of formatting restrictions – the text cannot be indented, and inserted tables and images cannot be formatted.
This format is used to compress TIFF images when sending them via fax machines. This format helps reduce the data transmission time. Group 3 eliminates redundant data during compression in order to reduce file size. The standard 10:1 compression ratio may be increased to the user's preferences, but it can lead to a significant loss of image quality.