What is coreaudiod on Mac?

What coreaudiod does

coreaudiod (/usr/sbin/coreaudiod, running as _coreaudiod) is the Core Audio server. It owns every input and output device: the built-in speakers and mics, USB interfaces, Bluetooth headphones, AirPlay and virtual devices. It mixes the audio from all apps, converts sample rates, applies volume, and handles device switching. Since macOS 14.2 it also runs process taps, the API that lets apps capture or adjust another app’s audio.

Audio drivers called HAL plug-ins load inside it. That is why a third-party driver can make coreaudiod itself slow or unstable.

Why it uses CPU

• Virtual audio devices: drivers from Zoom, Teams, Loopback, BlackHole, Krisp, Boom and similar tools run inside coreaudiod. Old or abandoned ones are the top cause of trouble.
• Sample-rate conversion: a device at 44.1 kHz while apps play at 48 kHz (or the reverse) adds work and can cause pops.
• Many simultaneous streams: browser tabs, calls and music at once.
• Bluetooth switching: AirPods moving between devices or switching to the headset profile during a call.
• Low buffer sizes used by audio production apps.

How to make it calm down

List installed HAL plug-ins and remove the ones you don’t use:

ls /Library/Audio/Plug-Ins/HAL ~/Library/Audio/Plug-Ins/HAL 2>/dev/null

Use the app’s uninstaller if it has one; otherwise delete the .driver bundle and restart coreaudiod.

Restart the audio server:

sudo killall coreaudiod

Check and set sample rates in Audio MIDI Setup (Applications › Utilities). 48 kHz is a good default for calls and video. Then confirm which device is active:

system_profiler SPAudioDataType | grep -E 'Default|:$|Sample'

If an app is holding audio open while silent, quit it and see if coreaudiod drops. Browsers with a muted video tab still stream.

When to worry

The real one lives in /usr/sbin:

codesign -dv --verbose=2 /usr/sbin/coreaudiod 2>&1 | grep -E 'Identifier|Authority'

What deserves attention is what’s loaded into it. An audio driver you don’t remember installing can capture system audio. Remove unknown drivers from the HAL folders above. If your microphone is in use and you don’t know why, see which app is using the microphone.

Seeing it in Stat Space

Stat Space’s Volume tab shows every app playing audio with a per-app volume slider (0–150%), and a “Mic in use by X” banner when something has the microphone. It uses Core Audio process taps, so there is no driver to install into coreaudiod, and a tap runs only for an app whose volume isn’t at 100% and only while it plays.