Nextcloud Talk will be DESY’s central chat service for quick, informal communication with colleagues starting mid-April 2026 – whether in 1-to-1 conversations or project-/group-related discussions. Thanks to its integration with Nextcloud (DESY Sync & Share), you can directly access cloud documents in the chat and manage permissions.

The status of the migration process from Mattermost to Nextcloud Talk is outlined on this page.

Documentation about Nextcloud Talk

Documenatation about Nextcloud Talk can be found on the following sources:

• Official Nextcloud Talk Documentation
• Further information about functions in Nextcloud Talk in DESY Wiki
   

Feature Scope

The current focus is on the chat module of Nextcloud Talk. The calling feature is limited to 1-to-1 calls. For group calls and video conferences, ZOOM and DFNconf can still be used.

Prerequisites

To use Nextcloud Talk, you must have permissions to access DESY Sync & Share (resource "owncloud"). If you cannot log in at https://syncandshare.desy.de, please contact your group administration or the UCO to obtain access.

Additionally, you need permission to use Nextcloud Talk (resource "sas-talk"). By default you should have access. However, if you do not see the Nextcloud Talk icon (as shown in the "Web client" section) after logging in, please contact your group administration or the UCO.

Usage Options for Nextcloud Talk

In the following sections the options for using Nextcloud Talk are described briefly.

Access

Nextcloud Talk is available as a web client and as a desktop or mobile app. Access requires your DESY login credentials (accountname and password) as well as your second factor (TOTP token in your authenticator app).

Webclient

The service is accessible at https://syncandshare.desy.de/. The Nextcloud Talk icon (speech bubble) can be found at the top of the main navigation bar:

Desktop/Mobile App

For Linux, Windows, and macOS, the Talk app is available via the central software distributions (DSM, Munki, DESY Linux repositories). All necessary information can be found in the DESY Wiki.

Depending on the app, the following server address must be entered:

• https://syncandshare.desy.de or
• syncandshare.desy.de
   

Other addresses through which the service is accessible (e.g., sas.desy.de or https://sas.desy.de) will not work here.

Important Notes on Data Shared via Nextcloud Talk

Data shared in Nextcloud Talk behaves exactly like all other data shared via Sync & Share. In this context, please carefully read the instructions in the user documentation.

Background

The coronavirus situation made a dedicated, DESY-wide messaging (chat) service increasingly important. As a result, Mattermost was initially made available temporarily from April 15, 2020, following a decision by the DESY Directorate.

A re-evaluation in August 2026—due to the expiration of the Mattermost license—confirmed a continued need for chat services. For long-term use, improvements in user-friendliness, maintenance, and cost efficiency were required. Nextcloud Talk emerged as the most suitable solution, thanks to its integration with the existing Nextcloud service.

Further Hints

• The messaging service is based on servers in the DESY data center.

• Use of the messaging service is voluntary.

• The messaging service is intended as a supplement to official communication and documentation channels such as email and websites.

• Confidential data, especially personal data, should not be exchanged via the messaging service.