Calibre

Calibre is free and open-source e-book management software designed to organize, convert, and read e-books across multiple devices. It runs on Windows, macOS, and Linux, and provides a single library for managing large collections of e-books and other digital documents.

Key features include metadata management, a built-in e-book viewer, and comprehensive format conversion. Calibre can convert between formats such as EPUB, MOBI, AZW3, PDF, and HTMLZ, edit metadata and cover art, and organize books by author, series, tags, and rating. It can also download news from the web and convert it into e-book form.

The software includes a content server that makes the library accessible from a web browser or other devices on a network, and it supports wireless transfer to compatible e-readers and devices in addition to USB connections. An integrated e-book editor provides editing of HTML and CSS within e-books.

Calibre is released under the GNU General Public License and is maintained by an open-source community led by its founder, Kovid Goyal. The project emphasizes user control over library organization, metadata, and format conversion, with ongoing development and feature additions.