Mobipocket

Mobipocket is an e-book format and the name of a software suite developed by the company Mobipocket SA. The company produced the Mobipocket e-book format, along with applications such as Mobipocket Reader and Mobipocket Creator. In 2005, Amazon.com acquired Mobipocket, incorporating its format and technology into the Kindle ecosystem.

The Mobipocket format is a proprietary e-book format that originated from the Open eBook standard. It stores content in a binary container and uses HTML-like markup with CSS for layout, supporting images, metadata, bookmarks, annotations, and a table of contents. Some MOBI files can include digital rights management (DRM) protection issued by Mobipocket or its partners. The format became popular on mobile devices and was widely used by Kindle devices as the basis for early Kindle formats; Kindle uses variants such as AZW, AZW3, and older MOBI-derived files, often with Amazon DRM.

Mobipocket's software lineup included Mobipocket Reader, a cross‑platform e-reader for Windows, Palm OS, Windows Mobile, and other platforms, and Mobipocket Creator, a conversion tool that exported documents into the MOBI format. After the acquisition, Amazon integrated the technology into its Kindle line, while the original Mobipocket products gradually faded from active development.

Today, the MOBI format continues to influence Kindle-compatible e-books, and modern e-book management tools such as Calibre can import and export MOBI files. The format's legacy remains in the lineage of Kindle formats, even as newer Kindle formats have evolved.