Bitfocus Companion is a fantastic free tool which allows users to map many custom actions to controllers such as the Elgato Stream Deck and other USB buttons.

To set up CaptionKit signals with Companion, first you will need a CaptionKit API key. Follow this guide if you haven't set one up yet.

Once you have your API key for CaptionKit, open the Companion dashboard to the Connections tab. Add a new Generic: HTTP Requests type connection.

On the connection edit panel, label it as CaptionKit and add the following Base Url:

https://api.captionkit.io/v2/signal?key=API_KEY replacing API_KEY with your CaptionKit API key. Click Save.

Open the Buttons tab and add button for your CaptionKit signal. Give the button a label.

Under the Press actions heading, click the 📂 icon to add a new action. Select CaptionKit > GET from the dropdown.

Within the action edit panel, add your preferred signal parameter. This should be in the format of &event=SIGNAL_NAME, for example: &event=captions:stream:start

You can find a full list of signals here.

Once the action is set up, test your button by clicking ▶️ Test at the top of the button edit panel. If you have CaptionKit open and have turned on Signals, you should see the app respond to the signal almost immediately.