.mobi File — Mobipocket eBook

MOBI is an e-book file format created by Mobipocket SA, later acquired by Amazon. The format is based on the Open eBook standard with extensions for DRM, JavaScript, and advanced formatting. MOBI files use a PDB (Palm Database) container and support text reflowing, bookmarks, annotations, corrections, and basic formatting through a subset of HTML. Amazon adopted and extended the MOBI format for the Kindle ecosystem, creating related formats like AZW and KF8. While Amazon has increasingly moved toward the newer KF8/AZW3 format that supports HTML5 and CSS3, MOBI files remain compatible with all Kindle devices and the Kindle reading apps. The format includes support for dictionary lookup, embedded images, and metadata like cover art, title, and author information. MOBI files can be created from HTML, text, or converted from EPUB using tools like Calibre. The format has a maximum file size limit and limited support for complex layouts and tables.