Matrix is a versatile protocol for communication. Similar to ActivityPub, which Mastodon uses, Matrix supports federation. Thus, by self-hosting, you’re using your own server whilst also being able to use your own domain.

Setup

Assuming Docker is installed, the first step is to generate the configuration file.
The following command will generate a configuration file in ./synapse-data. Change matrix.example.com to the domain that will be used. If you’re running in Powershell, replace \ with ^

docker run -it --rm \
    -v $(pwd)/synapse-data:/data \
    -e SYNAPSE_SERVER_NAME=matrix.example.com \
    -e SYNAPSE_REPORT_STATS=no \
    matrixdotorg/synapse:latest generate

Configuration

Running the server now would result in a problem; registration and federation are not currently set up.

Registration

By default, registration is disabled. To enable it, edit ./synapse-data/homeserver.yaml and add the following:

enable_registration: true
enable_registration_without_verification: true

However, this is not recommended as this can lead to spam. Instead, some verification method should be used if registration is to be enabled. Using reCAPTCHA is one option. The Synapse documentation has a tutorial regarding this.

Federation

Federation allows Matrix servers to communicate. By default, it’s expected that the server is run on port 8448 with TLS. However, in some scenarios, this may not be the configuration. For example, I run Synapse in Docker on port 8007. On the host, Nginx is installed with the following configuration, with a different hostname, in /etc/nginx/sites-available/matrix-federation:

server {
    listen 8008;
    location /.well-known/matrix/server {
        add_header Content-Type application/json;
        return 200 '{"m.server": "matrix.example.com:443"}';
    }
    location / {
        proxy_set_header X-Forwarded-For $remote_addr;
        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection "Upgrade";
        proxy_pass http://localhost:8007;
    }
}

I use Cloudflare tunnel to proxy my Matrix subdomain, on port 443, to <host IP>:8007. However, a similar Nginx config can be used for federation as well. Just make sure that http://localhost:8007 points to the Docker container and matrix.example.com:443 points to the address where Matrix can be accessed from outside your network.

Running the Server

The following command runs the server on port 8007. Note that you will need a client to use it.

docker run -d --name synapse \
    --name synapse \
    --restart unless-stopped \
    -itd \
    -v $(pwd)/synapse-data:/data \
    -p 8007:8008 \
    matrixdotorg/synapse:latest

One more thing

This is a simple setup and configuration. This is similar to how I run my Synapse server (at the time of writing). However, it isn’t necessarily the best configuration.