Mastodon client registration is not done via ther web interface, but by talking to the API directly. In the example below, we use curl to register a new client.

Optionally check that you have jq installed on your system. You can normally install this with brew, apt-get, yum or chocolatey. If you don't have jq installed, you can remove it from the command below.

Run the following curl command in a terminal to get the Mastodon client id and client secret.

curl -X POST -sS https://mastodon.social/api/v1/apps -F "client_name=YourAppName" -F "redirect_uris=http://localhost:4200/integrations/social/mastodon" -F "scopes=write:statuses write:media profile" | jq

This will give you output that looks something like this;

{
  "id": "1234567890",
  "redirect_uris": [
    "http://localhost:4200/integrations/social/mastodon"
  ],
  ...
  "client_id": "your_client_id",
  "client_secret": "your_client_secret"
}

Make a note of your client_id and client_secret and add them to your .env file.

MASTODON_CLIENT_ID="shown in the output from the above command"
MASTODON_CLIENT_SECRET="shown in the output from the above command"

Stop Postiz if it is running, and then start it using the .env file with the Mastodon details. Click through the new channel setup and you should be asked to login on Mastodon.