Main Goals

Radicale is a complete calendar and contact storing and manipulating solution. It can store multiple calendars and multiple address books.

Calendar and contact manipulation is available from both local and distant accesses, possibly limited through authentication policies.

It aims to be a lightweight solution, easy to use, easy to install, easy to configure. As a consequence, it requires few software dependencies and is pre-configured to work out-of-the-box.

Radicale is written in Python. It runs on most of the UNIX-like platforms (Linux, *BSD, macOS) and Windows. It is free and open-source software.

What Radicale Will Never Be

Radicale is a server, not a client. No interfaces will be created to work with the server, as it is a really (really really) much more difficult task.

CalDAV and CardDAV are not perfect protocols. We think that their main problem is their complexity, that is why we decided not to implement the whole standard but just enough to understand some of its client-side implementations.

CalDAV and CardDAV are the best open standards available and they are quite widely used by both clients and servers. We decided to use it, and we will not use another one.

Technical Choices

Important global development choices have been decided before writing code. They are very useful to understand why the Radicale Project is different from other CalDAV and CardDAV servers, and why features are included or not in the code.

Oriented to Calendar and Contact User Agents

Calendar and contact servers work with calendar and contact clients, using a defined protocol. CalDAV and CardDAV are good protocols, covering lots of features and use cases, but it is quite hard to implement fully.

Some calendar servers have been created to follow the CalDAV and CardDAV RFCs as much as possible: Davical, Baïkal and Darwin Calendar Server, for example, are much more respectful of CalDAV and CardDAV and can be used with a large number of clients. They are very good choices if you want to develop and test new CalDAV clients, or if you have a possibly heterogeneous list of user agents.

Even if it tries it best to follow the RFCs, Radicale does not and will not blindly implements the CalDAV and CardDAV standards. It is mainly designed to support the CalDAV and CardDAV implementations of different clients.


Radicale is designed to be simple to install, simple to configure, simple to use.

The installation is very easy, particularly with Linux: one dependency, no superuser rights needed, no configuration required, no database. Installing and launching the main script out-of-the-box, as a normal user, are often the only steps to have a simple remote calendar and contact access.

Contrary to other servers that are often complicated, require high privileges or need a strong configuration, the Radicale Server can (sometimes, if not often) be launched in a couple of minutes, if you follow the tutorial.


The CalDAV RFC defines what must be done, what can be done and what cannot be done. Many violations of the protocol are totally defined and behaviours are given in such cases.

Radicale often assumes that the clients are perfect and that protocol violations do not exist. That is why most of the errors in client requests have undetermined consequences for the lazy server that can reply good answers, bad answers, or even no answer.


Radicale has been started as a (free topic) stupid school project replacing another (assigned topic) even more stupid school project.

At the beginning, it was just a proof-of-concept. The main goal was to write a small, dirty and simple CalDAV server working with Lightning, using no external libraries. That’s how we created a piece of code that’s (quite) easy to understand, to use and to hack.

The first lines have been added to the SVN (!) repository as I was drinking (many) beers at the very end of 2008 (Python 2.6 and 3.0 were just released). It’s now packaged for a growing number of Linux distributions.

And that was fun going from here to there thanks to you!