Radicale — Simple CalDAV and CardDAV Server

Introduction

Radicale is a minimalist CalDAV and CardDAV server that lets you sync calendars, contacts, and to-do lists across all your devices. It runs as a single Python process with file-based storage and requires almost no configuration.

What Radicale Does

• Serve calendars (CalDAV) and contacts (CardDAV) over HTTP/HTTPS
• Support multiple users with per-user collections
• Store data as standard iCalendar and vCard files on disk
• Handle concurrent access with file-level locking
• Authenticate users via htpasswd, LDAP, or custom scripts

Architecture Overview

Radicale is a pure Python application with no external dependencies beyond the standard library. It runs a built-in WSGI server and stores each calendar and address book as a directory of iCalendar or vCard files. A JSON-based internal index accelerates queries without requiring a database.

Self-Hosting & Configuration

• Install via pip or run the official Docker image
• Set the storage path and authentication method in a TOML config file
• Use htpasswd files for simple user management
• Place behind Nginx or Caddy for TLS termination
• Back up by copying the storage directory

Key Features

• Zero external dependencies — runs anywhere Python is available
• File-based storage with no database to maintain
• Works with any CalDAV/CardDAV client: Thunderbird, iOS, Android DAVx5, macOS Calendar
• Multi-collection support for separate work and personal calendars
• LDAP authentication plugin for enterprise environments

Comparison with Similar Tools

• Baikal — PHP-based with a web UI; Radicale is lighter and needs no web server
• Nextcloud — full-featured cloud suite; Radicale does one thing well with minimal resources
• DAViCal — PostgreSQL-backed; Radicale uses flat files and needs no database
• Google Calendar — cloud-hosted; Radicale keeps all data on your server

FAQ

Q: Which clients work with Radicale? A: Any standard CalDAV/CardDAV client, including Thunderbird, Apple Calendar, iOS Contacts, DAVx5 on Android, and GNOME Calendar.

Q: Does it support shared calendars? A: Yes. Multiple users can access the same collection with appropriate permissions.

Q: How do I back up my data? A: Copy the storage directory. Each calendar is a folder of plain-text iCalendar files.

Q: Can it handle thousands of contacts? A: Yes. The internal index keeps lookups fast even with large address books.

Sources

• https://github.com/Kozea/Radicale
• https://radicale.org