How to control OBS monitoring volume separately on Mac

OBS monitoring plays through your Mac's single output device, so its level rides the same master as every other app — and OBS's own source faders move the stream and the monitor together. To make what you hear from OBS quieter or louder without changing the level your viewers get, control OBS's app volume at the OS layer with a per-app mixer, and leave the source faders for the mix your audience hears.

Monitoring is how you hear your own sources in OBS — the game, the music bed, a guest on a call — before or while they go out to the recording or stream. On a Mac it lives under Settings → Audio → Monitoring Device, and per source under Advanced Audio Properties. The confusion starts when "turn the monitor down" and "turn the stream down" turn out to be the same knob, or when OBS ends up louder in your ears than your call, your chat, or your music. Here's how the pieces actually fit, and the two honest ways to get a monitoring level you control on its own.

What "monitoring volume" means in OBS

OBS has two audio destinations. One is the recording or stream — the internal mix OBS encodes and sends to a file or to Twitch, YouTube, and the rest. The other is monitoring — audio OBS plays out through your Mac so you can hear it live. In Advanced Audio Properties (the mixer's gear menu, or Edit → Advanced Audio Properties) every source has an Audio Monitoring column with three settings:

• Monitor Off — the source goes to your stream/recording but you don't hear it in the monitor.
• Monitor Only (mute output) — you hear it, but it does not go to the stream.
• Monitor and Output — you hear it and it goes to the stream.

The Monitoring Device (Settings → Audio → Advanced) picks which output OBS uses for that monitor audio — your headphones, usually. So far so good: this is real per-source monitoring routing.

The catch: the source fader moves both at once

Here's what trips people up. Each source's volume fader in the OBS mixer controls its level for the monitor and for the stream at the same time. Pull a game source down because it's blasting your ears, and you've just made it quieter for your viewers too. There is no built-in "monitor at 40%, stream at 100%" slider per source. Monitor Only and Monitor and Output decide the routing; they don't give you two independent levels.

That's fine when your ears and your audience want the same balance. It's a problem the moment they don't — you want a loud, clear monitor of a quiet guest while keeping their broadcast level polite, or you simply want OBS's whole monitor sitting under your Slack and music so it doesn't drown your other apps while you work between scenes.

Option 1 — Split it inside OBS (free, fiddly)

You can decouple monitor from stream without leaving OBS, at the cost of setup. The usual moves:

• Set a source to Monitor Only and route the broadcast copy elsewhere, so the fader you touch only affects the monitor.
• Duplicate a source or use a filter so one instance feeds the stream and another feeds monitoring, then balance them separately.
• Add a per-source monitor filter (the community "Audio Monitor" plugin) that sends a source to a chosen device with its own level slider — genuinely per-source monitor volume, if you don't mind installing a plugin.

All of this works. None of it is fast, and none of it helps with the other half of the problem: OBS's monitor still plays out as one app on a Mac that only has a single master volume. Turn the system down to hear a caller and your OBS monitor ducks with it.

Option 2 — Control OBS's monitor volume as an app

Here's the useful part most streaming guides miss. The only OBS audio that ever reaches your Mac's output device is the monitor — the recording and stream are mixed internally and go straight to disk or the network. So if you control OBS's volume as an app at the OS layer, you're changing exactly what you hear from monitoring, and nothing about the levels your viewers get.

That's the layer macOS leaves empty. There's no native per-app volume mixer — the volume keys and the Sound menu set one master for everything. A per-app mixer adds it back, giving OBS its own level alongside Spotify, Discord, your browser, and system alerts, all in one place. Set OBS's monitor to sit under your music, or push it up over a quiet call, without ever opening Advanced Audio Properties or risking your broadcast mix.

Where the free tools and the paid ones land

For per-app volume on the Mac, the honest field looks like this. Background Music is free and open source, adds a per-app level list in the menu bar, and is a fine no-cost start — it can be finicky to install and lives entirely in a menu. SoundSource, from Rogue Amoeba, is deep and polished with per-app EQ and routing; SoundSource 6 is a $49 one-time purchase. Fader is $19.99 one-time and built around reaching the controls from the keyboard, which is the part that matters when you're live and your hands are busy.

None of these replace what OBS does internally — they don't touch your source faders, filters, or broadcast mix. They control the monitor, because that's the only OBS audio your Mac ever plays. Use OBS for the mix your viewers hear, and a per-app mixer for the mix in your own ears.

Why the keyboard matters when you're live

Mid-stream, a menu-bar slider is five actions: reach the menu bar, click the icon, find the OBS row, drag it, dismiss. That's a lot when a guest suddenly clips or a track comes in hot. Fader's approach is to make the keyboard the mixer — hit a toggle hotkey and letter keys become faders, so "OBS monitor down two notches" is a keystroke from inside OBS, your browser, or your chat, without moving your mouse off the scene. If you're setting up a full rig, our streamer's Mac audio setup without hardware walks through the whole thing.

What about sending OBS somewhere else entirely?

Volume's close cousin is routing — sending OBS's monitor to a specific output while everything else plays elsewhere, say monitoring in your headset while music stays on desk speakers. macOS sets one output for everything by default, so per-app routing also needs a third-party tool. If that's the real goal, read how to send an app's audio to a different output on Mac.

Bottom line

Inside OBS, monitoring routing is per source but the volume fader isn't — it moves your ears and your stream together. To split them, you either wire up Monitor Only routing and filters inside OBS, or you control OBS's monitor as an app on the Mac. Since the monitor is the only OBS audio your Mac plays, a per-app mixer changes what you hear and leaves your broadcast mix untouched. For a level you can ride in a keystroke while you're live, that's exactly what Fader is built for.