Radicale

Radicale is a small CalDAV and CardDAV server for sharing calendars, to-do lists, and contact lists over CalDAV, CardDAV, and HTTP. It supports events, todos, journal entries, and business cards, and stores data on the file system in a simple folder structure. It can be extended with plugins and is GPLv3-licensed free software.

The server provides flexible authentication options, including htpasswd-based users files, and can limit access through authorization rules. It supports TLS for secure connections and works with many CalDAV and CardDAV clients, including DAVx⁵, OneCalendar, GNOME Calendar, Contacts Evolution, KDE PIM Applications, Thunderbird, InfCloud, CalDavZAP, and CardDavMATE. Configuration can be provided through config files or command-line arguments, with options for server addresses, storage paths, authentication, rights, logging, and connection limits. It can run as a service on Linux with systemd, on Windows with NSSM, or behind a reverse proxy or WSGI server, and supports versioning collections with Git. Plugin development is supported for authentication, rights management, web, and storage extensions.