MOBI is a file format primarily used for eBooks, designed to be compatible with various devices, especially those from Amazon. It allows for reflowable text, meaning the content can adjust to fit different screen sizes, enhancing readability on devices like the Kindle. Originally developed by Mobipocket, MOBI files support features such as bookmarks, annotations, and digital rights management (DRM). This format is popular among authors and publishers for distributing eBooks, as it provides a user-friendly experience for readers while maintaining the integrity of the content.