Radicale

Radicale is an open-source CalDAV and CardDAV server designed for lightweight use. Implemented in Python, it aims to be standards-compliant and easy to install, suitable for personal calendars and contact books or small teams. The server exposes resources via CalDAV for calendars and CardDAV for address books, using WebDAV semantics for resource management. Clients synchronize data using the iCalendar (.ics) and vCard (.vcf) formats.

Radicale stores data in a local storage directory by default, with a per-user namespace for calendars and address books. The storage layout is simple and portable, which facilitates backups and migrations. The project provides a minimal configuration file radicale.conf to control server behavior, including authentication, access control, and storage location. Authentication methods typically include basic and digest HTTP authentication, with optional anonymous access configured per resource. Access control lists can restrict who can read or modify specific calendars or address books.

Radicale can run as a standalone HTTP server or be integrated behind a WSGI server and a reverse proxy, and it can operate with a small resource footprint suitable for personal use or small organizations. It is compatible with major CalDAV/CardDAV clients such as Apple Calendar, Mozilla Thunderbird with Lightning, Evolution, and Davx5 on Android, among others.

The software is distributed as free/open-source and is maintained by its community with contributions from users. It emphasizes simplicity, a small footprint, and adherence to open standards.