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What is radicale?

kozea/radicale — explained in plain English

Analysis updated 2026-06-26

★ 4,648PythonAudience · ops devopsComplexity · 3/5LicenseSetup · moderate

In one sentence

A lightweight self-hosted server for calendars, to-do lists, and contacts that stores everything as plain files and works with any CalDAV or CardDAV app on your phone or desktop.

Mindmap

mindmap
  root((radicale))
    What it does
      CalDAV server
      CardDAV server
    Data
      Plain file storage
      Easy backups
    Features
      Optional auth
      TLS encryption
      Plugin support
    Audience
      Self-hosters
      Small teams
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What do people build with it?

USE CASE 1

Self-host your calendar and contacts instead of storing them with Google or Apple

USE CASE 2

Sync events and tasks between your phone calendar app and a home server without a cloud subscription

USE CASE 3

Run a shared calendar server for a small team or family using apps they already have installed

USE CASE 4

Extend Radicale with a custom plugin to add authentication or storage behavior not included by default

What is it built with?

PythonCalDAVCardDAVTLS

How does it compare?

kozea/radicalemichael-lazar/rtvthiojoe/yt-spammer-purge
Stars4,6484,6474,649
LanguagePythonPythonPython
Setup difficultymoderateeasymoderate
Complexity3/52/53/5
Audienceops devopsdevelopergeneral

Figures from each repo's GitHub metadata at analysis time.

How do you get it running?

Difficulty · moderate Time to first run · 30min
Free to use and distribute, but any changes you make and share must also be released under the same open-source license (GPL v3).

So what is it?

Radicale is a self-hosted server for calendars, to-do lists, and contact books. It speaks two open protocols: CalDAV (for calendar data) and CardDAV (for contacts). Once Radicale is running on your own machine or a rented server, any compatible app on your phone or desktop can connect to it and keep your data in sync automatically. Most mainstream calendar and contacts apps already support these protocols, so you do not need to install anything special on your devices. The design philosophy is minimal. There is no separate database to install. All data is stored as plain files in a regular folder on disk, which makes backups straightforward and the contents easy to inspect or move. Getting started does not require reading through pages of configuration. Radicale supports calendar events, to-do tasks, journal entries, and contact cards. It can optionally require usernames and passwords to restrict who can connect, and it can encrypt traffic with TLS if you want to secure connections from outside your local network. Both features are opt-in, so a basic personal install stays simple while a shared family or small-team setup can be locked down properly. The project can be extended with plugins for anyone who needs custom behavior beyond what ships by default. It works with a wide range of CalDAV and CardDAV clients across different platforms. Radicale is free and open-source software, released under the GPLv3 license. The README is intentionally short and links to a dedicated documentation website and a community wiki for setup instructions, troubleshooting, and advanced configuration details.

Copy-paste prompts

Prompt 1
Walk me through setting up Radicale on a Linux VPS so I can sync my iPhone calendar and contacts to my own server.
Prompt 2
How do I configure Radicale to require a username and password and use TLS so connections from outside my home network are secure?
Prompt 3
Show me how to connect the Apple Contacts app on macOS to a Radicale CardDAV server running on my local network.
Prompt 4
How do I write a Radicale storage plugin in Python that saves calendar data to a PostgreSQL database instead of plain files?
Prompt 5
How do I set up automatic backups of Radicale's plain-file data directory on a schedule?

Frequently asked questions

What is radicale?

A lightweight self-hosted server for calendars, to-do lists, and contacts that stores everything as plain files and works with any CalDAV or CardDAV app on your phone or desktop.

What language is radicale written in?

Mainly Python. The stack also includes Python, CalDAV, CardDAV.

What license does radicale use?

Free to use and distribute, but any changes you make and share must also be released under the same open-source license (GPL v3).

How hard is radicale to set up?

Setup difficulty is rated moderate, with roughly 30min to a first successful run.

Who is radicale for?

Mainly ops devops.

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