Open-source ebook library management application for Windows, macOS, and Linux.

The Calibre logo. It looks like four books standing as if on a shelf. The left one has a burgundy spine with “Calibre” printed on it. The next has a green spine with “Kovid Goyal” (the author of Calibre) printed on it. The last two are yellow and blue, and are leaning against the first two.

Calibre is a free and open source ebook library management application. It runs on Windows, macOS and Linux. It supports many formats and can convert ebooks between them. It can synchronize to many devices.

Calibre has plug-in interfaces for several features (conversion, downloading to devices, news feeds), which can be programmed in Python.

There is also a support forum on mobileread.com.