The MOBI file format is a proprietary ebook format developed by Mobipocket, based on the Open eBook standard. It was initially designed for mobile devices with limited processing power and storage. MOBI files can contain digital rights management (DRM) to protect copyrighted content. The format supports basic formatting, images, and annotations. It gained popularity due to its use by Amazon's Kindle devices before Amazon transitioned to its own AZW format, which is based on MOBI. While Amazon no longer directly supports MOBI for new Kindle content, it remains a widely used format for older ebooks and those distributed outside of the Kindle ecosystem. MOBI files can be read on various devices and platforms using dedicated ebook reader software. The format is relatively simple compared to more modern ebook formats like EPUB, but it remains a viable option for distributing text-based content.