A terminal client for the Mattermost chat system
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Matterhorn is a terminal client for the Mattermost chat system.

Quick Start

We provide pre-built binary releases for some platforms. Please see the release list to download a binary release for your platform that matches your server version:


To fetch a release and run Matterhorn, run the following commands (where VERSION and PLATFORM match your setup):

wget https://github.com/matterhorn-chat/matterhorn/releases/download/<VERSION>/matterhorn-<VERSION>-<PLATFORM>.tar.gz
tar xf matterhorn-<VERSION>-<PLATFORM>.tar.gz
cd matterhorn-<VERSION>-<PLATFORM>

When you run Matterhorn you’ll be prompted for your server information and credentials. At present matterhorn supports only username/password authentication.

Note: Version ABBCC.X.Y matches Mattermost server version A.BB.CC. For example, if your Mattermost server version is 3.6.0 then you would download matterhorn version 30600.2.4. See Our Versioning Scheme for details.


For configuration options you have two choices:

  • Interactive configuration entered on each program run
  • Configuration via stored settings in a config file

The first option is useful when trying out the program because you can get up and running without worrying about making a configuration. Once you’re ready to make your settings persistent, they can be added to a configuration file. An example configuration file can be found at sample-config.ini. Any settings omitted from the configuration will be obtained interactively at startup.

When looking for configuration files, matterhorn will prefer config.ini in the current working directory, but will look in the typical XDG configuration directories (you’ll probably want to use $HOME/.config/matterhorn/config.ini) and as a last resort look for a globally-accessible /etc/matterhorn/config.ini.

Using the Client

The user interface has three main areas:

  • Left: list of channels you’re in, and list of users in your team and their statuses (+ means online, - means away, and an absent sigil means offline)
  • Right: messages in the current channel
  • Bottom: editing area for writing, editing, and replying to messages

You can use built-in keybindings or /cmd-style commands to operate the client. To see available keybindings and commands, use the default binding of F1 or run the /help command.

To join a channel, use the /join command to choose from a list of available channels. To create a channel, use /create-channel. To leave a channel, use /leave-channel.

To see the members in the current channel, use the /members command.

To send a message, type it into the editor and press Enter to send. To send a multi-line message, toggle multi-line mode with the default binding M-e. Markdown syntax is accepted.

To edit your current message in an external editor ($EDITOR), use the default binding of M-k.

To preview the message you’re about to send (e.g. to check on how your Markdown syntax will be rendered), toggle preview mode with the default binding M-p.

To change channels, use /focus or one of the default bindings C-n (next channel), C-p (previous channel), C-g (fast channel switch).

To directly message another user, use /focus or C-g.

C-g channel switching mode does a substring match of the input text on the channel and usernames; metacharacters ^ and $ at the beginning or end of input, respectively, anchor the match in case of multiple matches.

To switch to the channel you were in prior to the current channel, use the default binding M-s (swap). The most recent channel is marked in the channel list with a “<” indicator.

To switch to the next channel with unread messages, use the default binding M-a.

To quickly show a list of URLs mentioned in the current channel and then open one in your local browser, use the default binding of C-o and configure the urlOpenCommand configuration setting.

To edit, delete, flag, or reply to a message, select a message with the default binding of C-s. Use the default binding of C-c to cancel these operations.

Messages that have been flagged can be viewed with either the /flags command or M-8. This view allows you to select and unflag particular messages, as well.

To enable spell-checking in the message editor, install Aspell and set enableAspell to True in your configuration. To override Aspell’s choice of master dictionary, set the aspellDictionary option to the name of the dictionary you’d like to use.


  • Channel creation, deletion, and membership management commands
  • Optimized channel-switching modes: M-a, M-s, and C-g
  • Message posting, editing, replying, and deletion
  • Markdown rendering
  • Convenient URL-opening with local browser
  • Secure password entry via external command (e.g. OSX keychain)
  • Yank verbatim content from messages into the system clipboard
  • Preview message rendering before sending
  • Optional smart quoting for efficient Markdown entry
  • Edit messages with $EDITOR
  • Message editor with kill/yank buffer and readline-style keybindings
  • Tab-completion of usernames, channel names, and commands
  • Spell-checking via Aspell
  • Syntax highlighting of fenced code blocks in messages (works best in 256-color terminals)
  • Flagging and unflagging of posts, which are then viewable with M-8 or /flags

Spell Checking Support

Matterhorn uses aspell to perform spell-checking of your message input. To use this feature:

  • Install aspell and ensure that your installation includes dictionaries corresponding to your LANG setting. To check this, ask aspell to check some input: $ echo stuff | aspell -a Error: No word lists can be found for the language "en". $ echo $LANG en_US If Aspell succeeds, the output will look like this: @(#) International Ispell Version 3.1.20 (but really Aspell *
  • Set enableAspell to True in your config.ini
  • Enter any message input in the message editor in matterhorn. After a short delay after you stop typing, misspelled words will turn red.


matterhorn is built with the provided install.sh script, which requires git and an appropriate ghc/cabal installation. (Although the name suggests installtion, this will just do a build in dist-newstyle.) This script will pull the appropriate repos and build the application. This is required for building Matterhorn since clones of some of our other dependencies may need to be locally available in deps/ in case important changes to those dependencies have not yet been released.

Our Versioning Scheme

Matterhorn version strings will be of the form ABBCC.X.Y where ABBCC corresponds to the Mattermost server version supported by the release. For example, if a release supports Mattermost server version 1.2.3, the ABBCC portion of the matterhorn version will be 10203. The X.Y portion of the version corresponds to our own version namespace for the package. If the server version changes, X.Y SHOULD be 0.0. Otherwise the first component should increment if the package undergoes major code changes or functionality changes. The second component alone should change only if the package undergoes security fixes or other bug fixes.


If you decide to contribute, that’s great! Here are some guidelines you should consider to make submitting patches easier for all concerned:

  • If you want to take on big things, let’s have a design/vision discussion before you start coding. Create a GitHub issue and we can use that as the place to hash things out. We’ll be interested to discuss any usability / UI, performance, or compatibility issues.
  • Please make changes consistent with the conventions already used in the codebase.
  • We follow a few development practices to support our project and it helps when contributors are aware of these. Please see PRACTICES.md for more information.

Frequently Asked Questions

  • Q: Does matterhorn support Gitlab authentication?
  • A: No. But we would be happy to work with contributors who are interested in investigating what this would take and/or implementing it. See the Contributing section for details.