# How to join ACDH Mattermost Mattermost is a messaging platform which allows a team to communicate via thematic channels or direct messages between members, all in its own, dedicated workspace. ACDH has adopted Mattermost as its preferred way of team communication and provides a self-hosted instance as as service to its cooperation projects. Please follow these instructions to become a member to your project’s Mattermost team: ## 1 Register at gitlab ACDH Mattermost uses GitLab for authentication. Going to you can either create a new gitlab account or log in with your existing [GitHub](https://github.com), [Google](https://google.com), [Twitter](https://twitter.com) or [Bitbucket](https://bitbucket.org/) credentials. Further on, you will use these credentials to access Mattermost. ## 2 Becoming part of the team Announce the email-address associated with your GitLab account to your main contact at ACDH or to , naming the project / team you want to join. Our admins will then add you to the respective mattermost team. ##3 Accessing Mattermost 1. Go to or directly to your team’s address `http://mattermost.acdh.oeaw.ac.at/{teamname}` and click on the „GitLab“ button 2. You will be shown the GitLab login form 3. Login with the account chosen in step 1 4. You should be able to see the project’s workspace. ## 3 Download the mattermost stand-alone client For ease of use we recommend downloading the mattermost client application at which is available for PC, Mac or Linux as well as for mobile devices.