AI narrator overlay for OBS
Colorcast adds a caption overlay for each line and can lower your game audio while the commentator speaks, so viewers hear every word.
Add the overlay
- In OBS, add a Browser source.
- Set the URL to
http://127.0.0.1:3847/overlay. Colorcast serves it from your PC while the app is running. - Size and place it like any other source. It shows the caption for each line and the AI badge.
The overlay is a normal browser source, so it works in Streamlabs Desktop and other apps that support one.
Duck your game audio
On the Audio page in Colorcast, connect OBS ducking (it uses obs-websocket, built into OBS Studio 28 and later) and choose which inputs to lower. Colorcast turns them down while a line plays and brings them back after. Ducking is part of Creator and Pro, and it needs OBS Studio: Streamlabs Desktop has no obs-websocket.
Route the voice
- Simplest: play narration on your normal output; OBS picks it up with desktop audio.
- Own track: send narration to a virtual cable (VB-Audio Cable, VoiceMeeter) and add it in OBS as its own audio input, so you can mix it or keep it off VOD tracks.
- Discord too: set the virtual cable as your Discord mic alongside your real one and your squad hears it.
If something's off
- The overlay is blank: check that Colorcast is running, then refresh the browser source.
- No voice on stream: confirm the output device on the Audio page and use Test. If you use a virtual cable, monitor it in OBS to hear it yourself.
Free tier, no card. The overlay works on every plan; the AI badge can be hidden on Creator and Pro.
Questions
Does the overlay work in Streamlabs Desktop?
Yes, as a browser source. Automatic ducking needs OBS Studio's obs-websocket.
Can I hide the AI badge?
On Creator and Pro, yes. On Free it stays on. Either way, we recommend telling viewers the commentator is AI.
Does the overlay need the internet?
The overlay page comes from the app on your PC. The lines themselves are written and voiced online.