Nextcloud offers CalDav Synchronizer for Outlook users

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aboutThanks to a collaboration btween the developers behind the Outlook CalDav Synchronizer and Nextcloud, Outlook users can now easily sync their events, tasks and contacts between Outlook and Nextcloud servers. Combined with DAVDroid for Android, your Nextcloud can handle Calendar, Contacts and Tasks for desktop and mobile clients. Protect your files, calendars and contacts in a safe private cloud and integrate them with Outlook and your Windows desktop!

About Outlook CalDav Synchronizer

This project was initially started as a master thesis project at the University of Applied Sciences Technikum Wien, Software Engineering Degree program. Motivated by what the team considered "deplorable quality of proprietary sync solutions", the goal was to develop a easy to use tool which can sync almost any CalDAV or CarDDAV server with Outlook. Outlook CalDav Synchronizer supports Outlook 2007 to Outlook 2016 and is Free and Open-Source Software (FOSS), licensed under AGPL 3 and developed by Alexander Nimmervoll and Gerhard Zehetbauer. You can find the project on Github and SourceForge.

What can it do

The only open source CalDAV and CardDAV plugin offers two-way sync for CalDAV calendars and tasks, CardDAV contacts and can also handle the Google native Contacts and Tasks API.

It will handles Outlook categories, mapping CalDAV server colors to Outlook category colors and syncing calendars and tasks to the categories. The plugin also handles timezones and recurring events with exceptions and can deal with Outlook custom properties.

Other features include:

  • SSL/TLS support, support for self-signed certificates
  • Proxy support
  • Auto discovery of calendars and address books
  • Configurable sync time range filter
  • Time-triggered-sync and sync changes from Outlook immediately
  • Use server settings from Outlook IMAP/POP3 account profile

NextCloud Integration Steps

If you have a Nextcloud server and are looking to integrate calendar and contacts in your Outlook client, follow the steps below and you'll be good to go.

Download the zip file from the website extract it into any directory and start setup.exe. You can change the default install path, but you need to use a directory on the C:</code> drive. Follow the instructions and restart Outlook after the installation is finished.

Next, you will see a ribbon CalDav Synchronizer in Outlook and can add synchronization profiles for you NextCloud calendars and address books:

In the Synchronization profiles dialog, press Add new profile:


and select the NextCloud profile type:

In the profile setup dialog you can configure the details of the sync profile:

First, you should enter a profile name and select and Outlook folder you would like to synchronize with your NextCloud calendar. You can either choose an existing Outlook calendar or create a new folder in the Outlook dialog accessible with the button in the Outlook settings.

Next, you should configure the server settings, the DAV url is prefilled with the default NextCloud DAV path and you should only change the hostname of your Nextcloud server, enter Username and Password and press Test or discover settings to start the auto discovery of all server resources:


Just select your server calendar you would like to sync and press OK.

If you know the correct calendar CalDAV url, you can also enter that directly into the DAV Url textbox or paste it from the NextCloud Calendar App, when selecting Link in the calendar properties. For the personal calendar it looks like

Furthermore, you can configure sync settings and intervals or keep the default settings which are automatic Two-Way-Sync every 30 minutes for all events from 30 days in the past to 180 days in the future.

If needed, you can configure network and proxy options or special mapping configuration parameters in the corresponding option pages.

After the configuration of the sync profile is finished you can start the synchronization with pressing Synchronize now in the CalDav Synchronizer ribbon and your Outlook calendar will be in sync with your NextCloud calendar.

Of course, you can add multiple sync profiles for different calendars.

For address books, the profile setup is similar, just choose an Outlook contacts folder for synchronization.

After synchronizing, your Outlook and server address book are in sync.

Should there be any errors or warnings during synchronization, you can check the Reports in the ribbon for hints as to what the problem might be.

Enjoy your Nextcloud Calendar, Contacts and Tasks in Outlook!


Amazing! Thanks for you awesome work. I will test it at some point!

As it was asked on social “what is this integration beyond just CalDAV and CardDAV support”, I thought I’d post the answer here:

of course, but there is always room to integrate better. As you might remember, we worked with the developers of the Android DAVDroid app to make it a one-click affair to set up calendar and contact syncing - we created an API to get the account details and they implemented support for it.

Now the CalDAV Synchronizer developers support the Nextcloud CalDAV URL, making it easier to set up syncing. What is also happening is that the synchronizer will take the idiosyncracies of our calendar and contacts apps into account. As you probably know, CalDAV and CardDAV aren’t such great and universally consistently implemented standards - essentially, each app speaks its own dialect and the app thus has to map things properly to Outlook.

Besides those, we’re looking at other ways to integrate. We have ideas but let’s first do work before we talk more!

I’m Using Akruto to sync Outlook with my Galaxy S7 via my Wi-Fi network. Can I sync my PC Outlook with Nextcloud using this CalDav Synchronizer and then use Akruto to transfer data to my smartphone? You can check all the features and specs of this software here.
Can those two solutions work with each other?

Why don’t you simply use CalDav Synchronizer for Outlook to sync your PC Outlook with your Nextcloud instance and something like DAVDroid to sync your Android(s) with that very same Nextcloud instance? With this setup you don’t need Akruto anymore and your Android(s) are always up-to-date wherever you are as long as you have access to the internet.

Thanks for your input!
I will give Akruto a chance and then switch to your solution if something goes wrong.

I’m having trouble with a self-signed certificate, which is supported according to the article.

When I go to test settings, it reads:

An error occurred while sending the request.
The underlying connection was closed: Could not establish trust relationship for SSL/TLS secure channel.
The remote certificate is invalid according to the validation procedure.

I generated a certificate with openssl according to this guide:

Is there a setting that I need to check?

Any help is appreciated.

1st sorry for my english,
2e Thank you this addon is very good !
3e For Mac user With outlook or mail can you make version for us ?

Best regards,

This actually works very well (for 1 person).

Warning for those trying to sync shared calendars from nextcloud to outlook, etc. I erased all of my appointments.

I have several people on our nextcloud instance share their calendar with me, but that doesn’t seem to import into Outlook easily.

I’m thinking I might have to create several distinct calendars in outlook, then manually setup profiles for each shared nextcloud calendar and map it to an outlook calendar.

Anybody try this with shared calendars? I’m just afraid to tell my users what to do in outlook and have them accidentally erase their calendars and have it replicate to the server. Could be bad.


Would love to use CalDav synchronizer on outlook but caldav sync makes ouitlook crash on startup! Had to disable calday sync to access outlook again.
Any idea where I can start investigation?

I like to share another Outlook add-in called EVO Collaborator for Outlook that works with Nextcloud. I think many Nextcloud users were migrating from ownCloud like my company. My company was using this Outlook add-in to sync with ownCloud before migration. Then, my boss asked me to consult EVO staff to see if they will support Nextcloud. EVO staff told me Nextcloud and ownCloud are basically the same on CalDAV and CardDAV infrastructure-wise. Thus, ECO is working on Nextcloud too. But a syntax for server URL must follow in format like this: https://nextcloud_server//remote.php/, Then, I tried it and it actually works.

I have the outlook app installed on my android phone. How do I add the calendar of NC?

The add-on works fine with outlook 2010 except for the free/tentative/busy status which doesn’t map to nextcloud.
When the status is set to free or tentative in either outlook or nextcloud and the event is edited on its counterpart, the status revert back to busy.

I’d like to use this add-on but the installation process requires administrator privileges (which I don’t have). Is there any option that could let me use CalDav Synchronize as a standard user ?


I came across the Outlook CalDav Synchronizer via the online Nextcloud Conference talks, very impressive work! I do understand the demand for a sync with Outlook, given it’s dominance on the Windows OS.
So here a possibly more fundamental question: I am wondering if the sync to (cloud-based) Outlook clients does not defy the rational of most Nextcloud users to have “calendars and contacts in a safe private cloud”? I am aware of options to encrypt the transfer and storage on some cloud solutions, are there any recommendations or validations for the peace-of-mind of users/admins from privacy-concerned (EU GDPR!) enterprises?


I like it, it worked on first try. But there is one thing I am missing and this is “sync this category only”.
I have my complete contact list on my Google account but only want to sync category “work” to Nextcloud and from there to Outlook. Is this in some way possible?


It is nice, but in Nextcloud 15 the presets for Nextcloud do not work anymore.
There is an error: DataAccess.WebDavClientException: Response status code does not indicate success: ‘415’ (‘Unsupported Media Type’).

With the default preset it works, but one can not choose a calendar.

I am working with Outlook 2007 and 2010 Clients using CalDav Synchronizer V 3.5, which should be the newest one right now. Nexcloud is running on the latest version also (15)…

We would like to sync both, contacts and calenders but we do have the following issues:

  • After first sync, for each contact, the birthday was synced into a separate calender. That’s fine, but it failed to sync the Date of the aniversary-field.
    It was not synced at all.
    I was expecting it to be either in an own calender “aniverseries” or into the birthday-calender.

  • We found, that some information, outlook stores on the “Details” tab (e.g. the name of the spouse oder the aniversary date) is not synced at all.
    Thats a problem, since we use to sync the contacts between the outlook-clients using nextcloud as a connecting server.
    So if my original entry contains a spouse, its synced to another client without it. If there is something changed and than synced back, the information may be lost on all clients…

So, not showing this information on the web frontend in nextcloud would not be our primary problem, as long, as the information is stored and synced correctly…



seems to be getting discussed closer here in the german part of the forum.
prolly no problem of caldav synchronizer.

Yes, I created that thread.
But thought, the topic maybe fits in here as well…

Right now, I am not shure, WHICH Part (nextcloud / caldav synchronizer / outlook) is causing the problem…