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Last Updated: 07-20-2026 07:21 PM (UTC)

Radicale

Calendars, to-do lists, journal entries, and contacts, synced over the open CalDAV and CardDAV standards nearly every client already speaks: Radicale is a small pure-Python server that works with Thunderbird, DAVx5 on Android, Apple Calendar and Contacts, GNOME, and many more. Its defining design choice is radical simplicity: there is no database. Events live as plain .ics files and contacts as .vcf files in an ordinary folder structure, which makes backup a copy command, migration a move, and disaster recovery a matter of reading text files. The server works out of the box with no complicated setup, then grows as needed: flexible authentication (htpasswd files among other methods), per-collection authorization rules, TLS-secured connections, and a plugin system for extending storage, auth, and rights handling. Built-in limits on parallel connections, file sizes, and failed authentication attempts harden it for network exposure behind a reverse proxy. A bundled web interface handles creating and managing calendars and address books - useful since many clients cannot create collections themselves. Maintained since 2011 with 140+ contributors, GPLv3-licensed, and light enough to run on the smallest VPS or a Raspberry Pi.

Radicale

Benefits

  • Your Schedule Off Big Tech's Servers
  • Calendars and contacts sync through open CalDAV/CardDAV standards to the clients you already use - without a Google or Apple account in the loop.
  • Backups Are Just File Copies
  • No database means data lives as portable .ics and .vcf files; rsync or a tarball is a complete, restorable backup.
  • Running in Minutes, Not Evenings
  • Works out of the box with no complicated configuration, then adds auth, TLS, and access rules only as you need them.
  • Fifteen Years of Boring Reliability
  • Maintained since 2011 with 140+ contributors and regular releases - infrastructure that stays out of the way.

Features

  • CalDAV and CardDAV
  • Events, to-dos, journal entries, and business cards served over the standard protocols plus plain HTTP.
  • Filesystem Storage
  • Plain .ics and .vcf files in a simple folder structure - no MySQL or PostgreSQL required.
  • Flexible Auth and Rights
  • Multiple authentication backends, per-collection authorization, and TLS-secured connections.
  • Broad Client Compatibility
  • Works with Thunderbird, DAVx5, Apple Calendar/Contacts, GNOME, and most standards-compliant clients.
  • Web Management Interface
  • Create and manage calendars and address books in the browser, covering what clients can't.
  • Plugin Extensibility
  • Swap or extend storage, authentication, and rights handling with Python plugins.