User Documentation




Radicale is written in pure Python and does not depend on any library. It is known to work on Python 2.6, 2.7, 3.1, 3.2, 3.3, 3.4 and PyPy > 1.9. The dependencies are optional, as they are only needed for various authentication methods [1].

Linux and MacOS users certainly have Python already installed. For Windows users, please install Python [2] thanks to the adequate installer.


Radicale can be freely downloaded on the project website, download section. Just get the file and unzip it in a folder of your choice.

CalDAV and CardDAV Clients

At this time Radicale has been tested and works fine with the latest version of:

More clients will be supported in the future. However, it may work with any calendar or contact client which implements CalDAV or CardDAV specifications too (luck is highly recommended).

Simple Usage

Starting the Server

To start Radicale CalDAV server, you have to launch the file called radicale.py located in the root folder of the software package.

Starting the Client


After starting Lightning, click on File and New Calendar. Upcoming window asks you about your calendar storage. Chose a calendar On the Network, otherwise Lightning will use its own file system storage instead of Radicale's one and your calendar won't be remotely accessible.

Next window asks you to provide information about remote calendar access. Protocol used by Radicale is CalDAV. A standard location for a basic use of a Radicale calendar is http://localhost:5232/user/calendar.ics/, where you can replace user and calendar.ics by some strings of your choice. Calendars are automatically created if needed. Please note that the trailing slash is important.

You can now customize your calendar by giving it a nickname and a color. This is only used by Lightning to identify calendars among others.

If no warning sign appears next to the calendar name, you can now add events and tasks to your calendar. All events and tasks are stored in the server, they can be accessed and modified from multiple clients by multiple users at the same time.

Lightning and Thunderbird cannot access CardDAV servers yet. Also, as of version 17.0.5 the SOGo Connector addon is not fully functionally and will create extra address book entries with every sync.


First of all, show the calendar page in Evolution by clicking on the calendar icon at the bottom of the side pane. Then add a new calendar by choosing in the menu File → New → Calendar.

A new window opens. The calendar type is CalDAV, and the location is something like http://localhost:5232/user/calendar.ics/, where you can replace user and calendar by some strings of your choice. Calendars are automatically created if needed. Please note that the trailing slash is important.

You can fill other attributes like the color and the name, these are only used for Evolution and are not uploaded.

Click on OK, and your calendar should be ready for use.


Switch to the contacts page and click File → New → Adress book. In the new window choose WebDAV as type and something like http://localhost:5232/user/addressbook.vcf/ as location. Remember to enter the correct username.


Tested with 4.8.3, you need one running on Akonadi for Cal/CarDav support.

The procedure below can also be done trough the sidebar "Calendar Manager". But to ensure it works for everyone this examples uses the menu-bar.

  1. Click Settings → Configure KOrganizer.
  2. Click on General → Calendars.
  3. Click on Add.
  4. Choose DAV groupware resource (and click OK).
  5. Enter your username/passord (and click on Next).
  6. Select Configure the resource manually (and click on Finish).
  7. Fill in a Display name.
  8. Fill in your Username and Password.
  9. Click Add.
  10. Choose CalDav.
  11. For remote URL enter http://myserver:5232/Username/Calendar.ics/
  12. Click Fetch.
  13. Select desired calendar.
  14. Hit OK.
  15. Hit OK again.
  16. Close the Configuration Window (Click OK).
  17. Restart Korganizer for the calendar to appear in the "Calendar Manager" sidebar (at least with version 4.8.3.)

You can add a address book analogously to the above instructions, just choose CardDav and http://myserver:5232/Username/AddressBook.vcf/ in step 10 and 11. Also, if you already have a calendar set up you can add an address book to its "DAV groupware resource" under Configure-Kontact → Calendar → General → Calendars → Modify. This way you don't have to enter username and password twice.


CalendarSync can be combined with any Android calendar app and can even store the calendars in existing Android calendars which are synced by other sync adapters. Of course it can also create its own calendars.

So, to sync using CalendarSync you will have to:

  • start the app,
  • press the Menu button,
  • select Create WebiCal,
  • choose to start with a guided configuration.

Then enter your URL, Username and Password. As URL please use http(s)://server:port/username/.

If you can use HTTPS depends on your setup. Please replace username with the name of your user account.

Press test connection button. If everything signaled as OK then press search calendars button, select the calendars which you want to sync, and press the configure calendar button at the top of the display. Your calendars are now configured.

You can then start the first sync by going back to the main screen of the app an pressing the Process Webicals button. Of course you can also configure the app at its preferences to sync automatically.


ContactSync is designed to sync contacts from and to various sources. It can also overtake contacts and push them to the server, also if they are only available on the device (local only contacts).

So to sync your contacts from the Radical server to your Android device:

  • start the app
  • press the Menu button,
  • select Create WebContact,
  • select guided configuration mode.

As URL please use http(s)://server:port/username/.

At the URL you will have to replace server:port and username so that it matches your specific setup. It also depends on your configuration if you can use HTTPS or if you have to use HTTP.

Press test connection button, if everything signaled as OK then press search address book button. Select the address books which you want to sync and press the configure address book button at the top of the display.

You can then start the first sync by going back to the main screen of the app and pressing the Handle WebContacts button. Of course you can also configure the app at its preferences to sync automatically.


CalDAV-Sync is implemented as sync adapter to integrate seamlessly with any calendar app and widget. Therefore you have to access it via Accounts & Sync settings after installing it from the Market.

So, to add new calendars to your phone open Accounts & Sync settings and tap on Add account, selecting CalDAV as type. In the next view, you have to switch to Manual Mode. Enter the full CalDAV URL of your Radicale account (e.g. http://example.com:5232/Username/) and corresponding login data. If you want to create a new calendar you have to specify its full URL e.g. http://example.com:5232/Username/Calendar.ics/. Please note that the trailing slash is important.

Tap on Next and the app checks for all available calendars on your account, listing them in the next view. (Note: CalDAV-Sync will not only check under the url you entered but also under http://example.com:5232/UsernameYouEnteredForLogin/. This might cause strange errors.) You can now select calendars you want to sync and set a local nickname and color for each. Hitting Next again brings up the last page. Enter your email address and uncheck Sync from server to phone only if you want to use two-way-sync.

Tap on Finish and you're done. You're now able to use the new calendars in the same way you were using Google calendars before.


Set up works like CalDAV-Sync, just use .vcf instead of .ics if you enter the URL, e.g. http://example.com:5232/Username/AddressBook.vcf/.


DAVdroid is a free and open-source CalDAV/CardDAV client that is available in Play Store for a small fee or in FDroid for free.

To make it working with Radicale, just add a new DAVdroid account and enter https://example.com/radicale/user/ as base URL (assuming that your Radicale runs at https://example.com/radicale/; don't forget to set base_prefix correctly).


aCal is a CalDAV client for Android. It comes with its own calendar application and does not integrate in the Android calendar. It is a "CalDAV only" calendar, i.e. it only works in combination with a CalDAV server. It can connect to several calendars on the server and will display them all in one calendar. It works nice with Radicale.

To configure aCal, start aCal, go to the Settings screen, select Server, then Add server. Choose Manual Configuration and select Advanced (bottom of the screen). Then enter the host name of your server, check Active, enter your user name and password. The Simple Domain of your server is the domain part of your fully qualified host name (e.g. if your server is myserver.mydomain.org, choose mydomain.org).

As Simple Path you need to specify /<user> where user is the user you use to connect to Radicale. Server Name is the fully qualified name of your server machine (myserver.mydomain.org). The Server Path is /<user>/.

For Authentication Type you need to specify the method you chose for Radicale. Check Use SSL if your Radicale is configured to use SSL.

As the last thing you need to specify the port Radicale listens to. When your server is configured you can go back to the first Settings screen, and select Calendars and Addressbooks. You should find all the calendars that are available to your user on the Radicale server. You can then configure each of them (display colour, notifications, etc.).

InfCloud, CalDavZAP & CardDavMATE
Because settings are the same for InfCloud, CalDavZAP and CardDavMATE
only InfCloud is used in description below.
Radicale configuration

Add/Modify the following section in Radicale main configuration file:

# Additional HTTP headers
Access-Control-Allow-Origin = *
Access-Control-Allow-Headers = User-Agent, Authorization, Content-type, Depth, If-match, If-None-Match, Lock-Token, Timeout, Destination, Overwrite, X-client, X-Requested-With
Access-Control-Expose-Headers = Etag

InfCloud needs read access for everybody (including anonymous users) on Radicale's root directory. If using Radicales rights management add the following section to rights file:

# Allow caldavzap, carddavmate and infcloud to work
user: .*
collection: /
permission: r

Additional you need to change [owner-write] section to use the same syntax for collection as shown in [public] section.

# Give write access to owners
user: .+
# collection: ^%(login)s/.+$    # DOES NOT WORK
collection: ^%(login)s(/.+)?$
permission: rw
InfCloud configuration

Inside InfCloud configuration file config.js you need to set globalNetworkCheckSettings like following example:

// href:
// put in here your protocol, host and port where Radicale is listening
// additionalResources:
// put in here a comma separated list of collections you want additionally look at.
// Don't forget '' around each collections name
var globalNetworkCheckSettings={
    href: 'https://host.example.com:5232/',
    hrefLabel: null,
    crossDomain: null,
    additionalResources: ['public'],
    forceReadOnly: null,
    withCredentials: false,
    showHeader: true,
    settingsAccount: true,
    syncInterval: 60000,
    timeOut: 30000,
    lockTimeOut: 10000,
    delegation: false,
    ignoreAlarms: false,
    backgroundCalendars: []
You can easily create them by directly calling the URL's from your browser:
Replace "http(s)" with the correct protocol, "host.example.com:5232" with you host:port where Radicale is running,
"user" with the correct login name or the shared resource name i.e. 'public',
"calendar.ics" and "addresses.vcf" with the collection names you want to use
and do NOT forget the '/' at line end.

iPhone & iPad

For iOS devices, the setup is fairly straightforward but there are a few settings that are critical for proper operation.

  1. From the Home screen, open Settings
  2. Select Mail, Contacts, Calendars
  3. Select Add Account…OtherAdd CalDAV Account
  4. Enter the server URL here, including https, the port, and the user/calendar path, ex: https://myserver.domain.com:3000/bob/birthdays.ics/ (please note that the trailing slash is important)
  5. Enter your username and password as defined in your server config
  6. Enter a good description of the calendar in the Description field. Otherwise it will put the whole servername in the field.
  7. Now go back to the Mail, Contacts, Calendars screen and scroll down to the Calendars section. You must change the Sync option to sync All events otherwise new events won't show up on your iOS devices!

In Contacts on iOS 6:

  1. From the Home screen, open Settings
  2. Select Mail, Contacts, Calendars
  3. Select Add Account…OtherAdd CardDAV Account
  4. As Server use the Radicale server URL with port, for example localhost:5232
  5. Add any User name you like (if you didn't configure authentication)
  6. Add any Password you like (again, if you didn't configure authentication)
  7. Change the Description to something more readable (optional)
  8. Tap Next
  9. An alert showing Cannot Connect Using SSL will pop up as we haven't configured SSL yet, Continue for now
  10. Back on the Mail, Contacts, Calendars screen you scroll to the Contacts section, select the Radicale server as Default Account when you want to save new contacts to the Radicale server
  11. Exit to the Home screen and open Contacts, tap Groups, you should see the Radicale server

In iCal 4.0 or iCal 5.0:

  1. Open the Preferences dialog and select the Accounts tab
  2. Click the + button at the lower left to open the account creation wizard
  3. As Account type select CalDAV
  4. Select any User name you like
  5. The Password field can be left empty (we did not configure authentication)
  6. As Server address use domain:port, for example localhost:5232 (this would be the case if you start an unconfigured Radicale on your local machine)

Click Create. The wizard will now tell you, that no encryption is in place (Unsecured Connection). This is expected and will change if you configure Radicale to use SSL. Click Continue.

The wizard will close, leaving you in the Account tab again. The account is now set-up. You can close the Preferences window.


In Contacts 7 (previously known as AddressBook):

  1. Open the Preferences dialog and select the Accounts tab.
  2. Click the + button at the lower left to open the account creation wizard.
  3. As Account type select CardDAV.
  4. Add any User name you like.
  5. The Password field can be left empty (if we didn't configure authentication).
  6. As Server address use domain:port, for example localhost:5232 (this would be the case if you start an unconfigured Radicale server on your local machine).
  7. Click Create. Contacts will complain about an Unsecured Connection if you don't have SSL enabled. Click Create again.
  8. You might want to change the Description of the newly added account to something more readable. (optional)
  9. Switch to the General tab in the preferences and select the Radicale server as Default Account at the bottom of the screen. It probably shows up as `domain:port or the name you choose if you changed the description. Newly added contacts are added to the default account and by default this will be the local On My Mac account.

You can find more information about syncEvolution and Radicale on the syncEvolution wiki page.

Nokia / Microsoft Windows Phones
  1. Go to "Settings" > "email+accounts"
  2. Click "add an account" > "iCloud"
  3. Enter random email address (e.g. "foo@bar" and "qwerty") > "sign in"
  4. A new account "iCloud" with the given email address appears on the list. The status is "Not up to date". Click the account.
  5. An error message is given. Click "close".
  6. Enter new and "real" values to the account setting fields:
    • "Account name": This name appears on the calendar etc. Examples: "Home", "Word", "Sauna reservation"
    • "Email address": Not used
    • "Sync contacts and calendar": Select the sync interval
    • "Content to sync": Uncheck "Contacts", check "Calendar"
    • "Your name": Not used
    • "Username": Username to your Radicale server
    • "Password": Password to your Radicale server
    • Click "advanced settings"
    • "Calendar server (CalDAV)": Enter the full path to the calendar .ics file. Don't forget the trailing slash. Example: https://my.server.fi:5232/myusername/calendarname.ics/

Don't forget to add your CA to the phone if you're using a self-signed certificate on your Radicale. Make the CA downloadable to Internet Explorer. The correct certificate format is X509 (with .cer file extension).

Complex Configuration

Installing the Server

You can install Radicale thanks to the following command, with superuser rights:

python setup.py install

Then, launching the server can be easily done by typing as a normal user:


Configuring the Server

Main Configuration File

The server configuration can be modified in /etc/radicale/config or in ~/.config/radicale/config. You can use the --config parameter in the command line to choose a specific path. You can also set the RADICALE_CONFIG environment variable to a path of your choice. Here is the default configuration file, with the main parameters:

# CalDAV server hostnames separated by a comma
# IPv4 syntax: address:port
# IPv6 syntax: [address]:port
# For example:, [::]:9999
# IPv6 adresses are configured to only allow IPv6 connections
hosts =
# Daemon flag
daemon = False
# File storing the PID in daemon mode
pid =
# SSL flag, enable HTTPS protocol
ssl = False
# SSL certificate path
certificate = /etc/apache2/ssl/server.crt
# SSL private key
key = /etc/apache2/ssl/server.key
# SSL Protocol used. See python's ssl module for available values
protocol = PROTOCOL_SSLv23
# Ciphers available. See python's ssl module for available ciphers
ciphers =
# Reverse DNS to resolve client address in logs
dns_lookup = True
# Root URL of Radicale (starting and ending with a slash)
base_prefix = /
# Possibility to allow URLs cleaned by a HTTP server, without the base_prefix
can_skip_base_prefix = False
# Message displayed in the client when a password is needed
realm = Radicale - Password Required

# Encoding for responding requests
request = utf-8
# Encoding for storing local collections
stock = utf-8

# Authentication method
# Value: None | htpasswd | IMAP | LDAP | PAM | courier | http | remote_user | custom
type = None

# Custom authentication handler
custom_handler =

# Htpasswd filename
htpasswd_filename = /etc/radicale/users
# Htpasswd encryption method
# Value: plain | sha1 | crypt
htpasswd_encryption = crypt

# LDAP server URL, with protocol and port
ldap_url = ldap://localhost:389/
# LDAP base path
ldap_base = ou=users,dc=example,dc=com
# LDAP login attribute
ldap_attribute = uid
# LDAP filter string
# placed as X in a query of the form (&(...)X)
# example: (objectCategory=Person)(objectClass=User)(memberOf=cn=calenderusers,ou=users,dc=example,dc=org)
# leave empty if no additional filter is needed
ldap_filter =
# LDAP dn for initial login, used if LDAP server does not allow anonymous searches
# Leave empty if searches are anonymous
ldap_binddn =
# LDAP password for initial login, used with ldap_binddn
ldap_password =
# LDAP scope of the search
ldap_scope = OneLevel

# IMAP Configuration
imap_hostname = localhost
imap_port = 143
imap_ssl = False

# PAM group user should be member of
pam_group_membership =

# Path to the Courier Authdaemon socket
courier_socket =

# HTTP authentication request URL endpoint
http_url =
# POST parameter to use for username
http_user_parameter =
# POST parameter to use for password
http_password_parameter =

# Git default options
committer = Radicale <radicale@example.com>

# Rights backend
# Value: None | authenticated | owner_only | owner_write | from_file | custom
type = None

# Custom rights handler
custom_handler =

# File for rights management from_file
file = ~/.config/radicale/rights

# Storage backend
# -------
# -------
# Value: filesystem | multifilesystem | database | custom
type = filesystem

# Custom storage handler
custom_handler =

# Folder for storing local collections, created if not present
filesystem_folder = ~/.config/radicale/collections

# Database URL for SQLAlchemy
# dialect+driver://user:password@host/dbname[?key=value..]
# For example: sqlite:///var/db/radicale.db, postgresql://user:password@localhost/radicale
# See http://docs.sqlalchemy.org/en/rel_0_8/core/engines.html#sqlalchemy.create_engine
database_url =

# Logging configuration file
# If no config is given, simple information is printed on the standard output
# For more information about the syntax of the configuration file, see:
# http://docs.python.org/library/logging.config.html
config = /etc/radicale/logging
# Set the default logging level to debug
debug = False
# Store all environment variables (including those set in the shell)
full_environment = False

# Additional HTTP headers
#Access-Control-Allow-Origin = *

This configuration file is read each time the server is launched. If some values are not given, the default ones are used. If no configuration file is available, all the default values are used.

Logging Configuration File

Radicale uses the default logging facility for Python. The default configuration prints the information messages to the standard output. It is possible to print debug messages thanks to:

radicale --debug

Radicale can also be configured to send the messages to the console, logging files, syslog, etc. For more information about the syntax of the configuration file, see: http://docs.python.org/library/logging.config.html. Here is an example of logging configuration file:

# Loggers, handlers and formatters keys

# Loggers names, main configuration slots
keys = root

# Logging handlers, defining logging output methods
keys = console,file

# Logging formatters
keys = simple,full

# Loggers

# Root logger
level = DEBUG
handlers = console,file

# Handlers

# Console handler
class = StreamHandler
level = INFO
args = (sys.stdout,)
formatter = simple

# File handler
class = FileHandler
args = ('/var/log/radicale',)
formatter = full

# Formatters

# Simple output format
format = %(message)s

# Full output format
format = %(asctime)s - %(levelname)s: %(message)s
Command Line Options

All the options of the server part can be changed with command line options. These options are available by typing:

radicale --help


Radicale comes with a WSGI support, allowing the software to be used behind any HTTP server supporting WSGI such as Apache.

Moreover, it is possible to use flup to wrap Radicale into a CGI, FastCGI, SCGI or AJP application, and therefore use it with Lighttpd, Nginx or even Tomcat.

Apache and mod_wsgi

To use Radicale with Apache's mod_wsgi, you first have to install the Radicale module in your Python path and write your .wsgi file (in /var/www for example):

import radicale
application = radicale.Application()

Next you have to create the Apache virtual host (adapt the configuration to your environment):

<VirtualHost *:80>
    ServerName cal.yourdomain.org

    WSGIDaemonProcess radicale user=www-data group=www-data threads=1
    WSGIScriptAlias / /var/www/radicale.wsgi

    <Directory /var/www>
        WSGIProcessGroup radicale
        WSGIApplicationGroup %{GLOBAL}
        AllowOverride None
        Order allow,deny
        allow from all

If you want to use authentication with Apache, you really should use one of the Apache authentication modules, instead of the ones from Radicale: they're just better.

Deactivate any rights and module in Radicale and use your favourite Apache authentication backend. You can then restrict the access: allow the alice user to access /alice/* URLs, and everything should work as expected.

Here is one example of Apache configuration file:

<VirtualHost *:80>
    ServerName radicale.local

    WSGIDaemonProcess radicale user=radicale group=radicale threads=1
    WSGIScriptAlias / /usr/share/radicale/radicale.wsgi

    <Directory /usr/share/radicale/>
        WSGIProcessGroup radicale
        WSGIApplicationGroup %{GLOBAL}

        AuthType Basic
        AuthName "Radicale Authentication"
        AuthBasicProvider file
        AuthUserFile /usr/share/radicale/radicale.passwd
        Require valid-user

        AllowOverride None
        Order allow,deny
        allow from all

        RewriteEngine On
        RewriteCond %{REMOTE_USER}%{PATH_INFO} !^([^/]+/)\1
        RewriteRule .* - [Forbidden]

If you're still convinced that access control is better with Radicale, you have to add WSGIPassAuthorization On in your Apache configuration files, as explained in the mod_wsgi documentation.


Authentication is possible through:

  • Courier-Authdaemon socket
  • htpasswd file, including list of plain user/password couples
  • HTTP, checking status code of a POST request
  • IMAP
  • LDAP
  • PAM
  • Remote user given by HTTP server

Check the [auth] section of your configuration file to know the different options offered by these authentication modules.

Some authentication methods need additional modules, see Python Versions and OS Support for further information.

You can also write and use a custom module handle authentication if you use a different technology.

Please note that these modules have not been verified by security experts. If you need a really secure way to handle authentication, you should put Radicale behind a real HTTP server and use its authentication and rights management methods.

Rights Management

You can set read and write rights for collections according to the authenticated user and the owner of the collection.

The owner of a collection is determined by the URL of the collection. For example, http://my.server.com:5232/anna/calendar.ics/ is owned by the user called anna.

The authenticated user is the login used for authentication.

5 different configurations are available, you can choose the one you want in your configuration file. You can also write and use a custom module handle rights management if you need a specific pattern.


Everybody (including anonymous users) has read and write access to all collections.


An authenticated users has read and write access to all collections, anonymous users have no access to these collections.

Owner Only

Only owners have read and write access to their own collections. The other users, authenticated or anonymous, have no access to these collections.

Owner Write

Authenticated users have read access to all collections, but only owners have write access to their own collections. Anonymous users have no access to collections.

From File

Rights are based on a regex-based file whose name is specified in the config (section "right", key "file").

Authentication login is matched against the "user" key, and collection's path is matched against the "collection" key. You can use Python's ConfigParser interpolation values %(login)s and %(path)s. You can also get groups from the user regex in the collection with {0}, {1}, etc.

For example, for the "user" key, ".+" means "authenticated user" and ".*" means "anybody" (including anonymous users).

Section names are only used for naming the rule.

Leading or ending slashes are trimmed from collection's path.


# This means all users starting with "admin" may read any collection
user: ^admin.*$
collection: .*
permission: r

# This means all users may read and write any collection starting with public.
# We do so by just not testing against the user string.
user: .*
collection: ^public(/.+)?$
permission: rw

# A little more complex: give read access to users from a domain for all
# collections of all the users (ie. user@domain.tld can read domain/\*).
user: ^.+@(.+)\..+$
collection: ^{0}/.+$
permission: r

# Allow authenticated user to read all collections
user: .+
collection: .*
permission: r

# Give write access to owners
user: .+
collection: ^%(login)s/.+$
permission: w

Git Support

Git is now automatically supported on Radicale. It depends on dulwich.

Configure Radicale

Radicale automatically detects the .git folder in the path you configured for the filesystem_folder variable in the [storage] section of your configuration file. Make sure a repository is created at this location or create one (using git init . for instance) else it won't work.

To summarize :

  • Configure your Git installation
  • Get Radicale and dulwich
  • Create the repository where your collections are stored
  • Run Radicale and it should work
How it works

Radicale will automatically commit any changes on your collections. It will use your git config to find parameters such as the committer and that's all.


A dulwich project ported on Python 3 exists but it seems that it doesn't follow the current api (committer is mandatory and not retrieved from the git config by default). Until this problem isn't fixed, the Git support for Radicale on Python 3 will not be ensured.

Python Versions and OS Support

TLS Support

Python 2.6 suffered a bug causing huge timeout problems with TLS. The bug is fixed since Python 2.6.6.

IMAP authentication over TLS requires Python 3.2.

Python 2.7 and Python 3.x do not suffer this bug.

Crypt Support

With the htpasswd access, many encryption methods are available, and crypt is the default one in Radicale. Unfortunately, the crypt module is unavailable on Windows, you have to pick another method on this OS.

IMAP Authentication

The IMAP authentication module relies on the imaplib module, available with 2.x versions of Python. However, TLS is only available in Python 3.2. Older versions of Python or a non-modern server who does not support STARTTLS can only authenticate against localhost as passwords are transmitted in PLAIN. Legacy SSL mode on port 993 is not supported.

LDAP Authentication

The LDAP authentication module relies on the python-ldap module, and thus only works with 2.x versions of Python.

PAM Authentication

The PAM authentication module relies on the python-pam module.

Bear in mind that on Linux systems, if you're authenticating against PAM files (i.e. /etc/shadow), the user running Radicale must have the right permissions. For instance, you might want to add the radicale user to the shadow group.

HTTP Authentication

The HTTP authentication module relies on the requests module.

Daemon Mode

The daemon mode relies on forks, and thus only works on Unix-like OSes (incuding Linux, OS X, BSD).