Matrix Chat

Last modified by Stefan Schwalb on 2023/08/28 20:39

What is Matrix?

Matrix user interface demo

Matrix is a chat system very similar to E-Mail, but instantaneous and secure.

  • You need to register an account at a provider (e.g., or
  • Whatever your provider is, you can talk to people using other providers
    • For example can communicate with!

  • In the same way you can use Outlook or Thunderbird with the same email account, you can use different Matrix apps for the same Matrix account!
    Several apps exist, but we're going to go with "Element" for the sake of simplicity, as it's among the most fully-featured Matrix apps on the market.

So people have their account on one server but can write messages to anyone on other servers.

Personal or group chats are end-to-end encrypted and not dependent on a central authority like most other tools (MS Teams, WhatsApp, Zoom, ...) - anyone can host a Matrix server.
All your messages are synced between all your devices  - web clients, desktop clients, smartphone apps.
For additional security, encryption keys of contacts can be verified and then stored as trusted. 

Home Server

Messages are stored and synced between home servers.

A user typically has one account on one homeserver.
You can use any homeserver of your choice - however for TUM, ITO offers two homeservers:

  • for CIT accounts:
  • for TUM accounts:

You only need to use one account and can communicate with any other homeserver of the world.

If you don't have a CIT or TUM account, you can use a public homeserver instead:

To use your home server, you have to use a client that communicates with your homeserver.


Element is our client of choice.

Make sure the home server is set correctly to your provider!

CIT: Homeserver: Username: CIT-ID (without  Password: CIT Password

TUM: Homeserver: Username: LRZ-ID (without or  Password: LRZ/TUM Password

Using Element for Matrix

Follow the official guide how to chat with Element 😎

You can create personal chats, group chats, and spaces for bundling multiple chatrooms to communicate with any other Matrix user in the world.

Invitation of TUM Users

When inviting TUM or CIT users to a chat, just enter the following Matrix IDs:

For CIT Accounts:     (e.g.

For TUM Accounts:     (e.g.

For other Accounts:  e.g.


The invitation will then appear in the Matrix client of the just-added user and must be accepted.

Search for User Names

To add a user to the user directory, he must become a member of a public chat room on the server, e.g. on, or share a private chat. Only after that his name will be displayed in the search field for persons.

Secure Backup

Since end-to-end encryption stores decryption keys only on clients (the "end"), logging out of the last client would mean loosing all messages.

Matrix allows to create a encrypted backup of the decryption keys on your homeserver - with a separate passphrase.

Matrix will ask you to set up your secure backup, and will request the password for the backup keys if needed.

More information is in the official documentation about private chats 🤓