MobipocketMOBI

Mobipocket MOBI is a proprietary e-book format developed by Mobipocket SA for use with its Mobipocket Reader family. It is used for distributing digital books and supports reflowable text, metadata, embedded images, and basic formatting.

Mobipocket SA founded its company in the late 1990s to create a portable e-book ecosystem. In 2005, Amazon acquired Mobipocket, and the MOBI format became widely used on Kindle devices, contributing to Kindle’s early library and DRM workflows.

A MOBI file typically contains a PalmDOC-like text section, a MOBI header with metadata such as title and author, and an EXTH header for extended metadata. It can include images and supports both reflowable text and fixed-layout content.

Compatibility remains strong on many Kindle devices and apps, although newer Kindle formats (AZW3/KF8) have largely supplanted MOBI for new titles. MOBI files are still supported by a range of e-reading software and can be converted to other formats using tools such as Calibre.

Related formats in the MOBI/PRC lineage include PalmDOC, PRC, AZW, AZW3, and KF8. The MOBI format thus stands as an important historical and transitional format in the evolution of digital libraries and Kindle-compatible e-books.