Run sudo killall coreaudiod in Terminal and macOS restarts its entire audio system in about a second, without a reboot. It clears stuck devices and odd sound caused by a bad sleep/wake cycle or a misbehaving app, though it changes no settings and won't fix a genuinely disconnected cable or muted app.
It is a real fix for a specific class of problem, not a general cure. Below is what the command actually does, how to run it, and how to tell when it is the wrong tool for what you are seeing.
What is Core Audio, and why would it need restarting?
Core Audio is the framework macOS uses to manage sound. The part that actually does the
work, running quietly in the background the whole time your Mac is on, is a process called
coreaudiod. Every speaker, headphone, microphone, and app that plays or records
audio talks to macOS through this one service. When it is working normally you never see it
or think about it.
Occasionally it gets into a bad state without anything being visibly broken. Nothing crashes, no error appears, but audio starts behaving oddly: a device shows the wrong status, sound comes out distorted, or an output that is definitely connected stops appearing in the list. This tends to follow a few specific triggers: certain sleep and wake cycles, an app that opened an audio stream and did not close it cleanly, or a driver hiccup. In all of these cases the hardware and macOS's settings are fine; it is the running service that has drifted out of sync with reality.
How do I restart Core Audio on a Mac?
Open Terminal, at Applications > Utilities > Terminal, and run this command:
sudo killall coreaudiod
Press return, enter your administrator password when prompted (it will not appear on
screen as you type, which is normal), and press return again. Nothing else needs typing.
killall stops the one running process you name, here coreaudiod,
and sudo is required because it is a system service. As soon as you confirm,
macOS notices the service has stopped and starts a new copy automatically, usually within
a second or two, with no need to launch anything else or restart the Mac.
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Download for MacWhat does this actually do, and not do?
It is not a reset of anything. No settings, no preferences, and no paired devices are
touched. All the command does is stop the audio service and let macOS start a replacement,
the same way quitting and reopening a stuck app restarts that app. The one unavoidable side
effect is that whatever was playing at that moment loses its connection to the old service:
a fraction of a second of silence, or occasionally a small click, before playback picks back
up through the new instance of coreaudiod.
One thing this does routinely clear is a Multi-Output or Aggregate Device built in Audio MIDI Setup, along with whichever output or input was selected at the time. Restarting the service means macOS reloads its device list from scratch, so a custom grouped setup is not always still selected afterwards, and you will likely need to pick it again from the Sound menu or rebuild it in Audio MIDI Setup.
When does restarting Core Audio genuinely help?
This fix is worth trying when the symptom points at the service being stuck in the wrong state, rather than at a real disconnection:
- A device is stuck showing as connected, or as disconnected, when it clearly is not. The Sound menu shows information that does not match reality.
- Sound became distorted or garbled right after waking from sleep. This is one of the most common triggers, since some sleep and wake cycles leave the service holding stale device information.
- An output or input has stopped appearing in the list, despite being plugged in or paired. The hardware is there; the service's view of it is not.
- General audio "weirdness" with no obvious cause. Crackling that started for no reason, a device that will not respond to volume changes, or apps disagreeing about which output is active.
When will this not help?
It is worth being precise about the limits, because this command gets recommended as a
catch-all far more often than it should be. Restarting coreaudiod cannot fix a
problem that is not actually about the daemon's state:
- A genuinely disconnected cable, dongle, or Bluetooth pairing. Reconnect the hardware first; the service was never the issue.
- Denied microphone or system audio permissions. Check System Settings > Privacy & Security instead. The service is doing exactly what it is being told.
- A muted app, or an app's own volume slider set to zero. That is app-level state, not something Core Audio controls.
- A genuine hardware fault, such as a blown speaker or a damaged port. No software restart changes what the hardware can physically do.
If the exact same symptom is still there a few seconds after running the command, that is a useful result: the cause sits somewhere other than the audio service, so check the cable, the permission, or the app instead of trying the command again.
For the full technical detail on the framework, see Apple's own Core Audio developer documentation.
Frequently asked questions
What does sudo killall coreaudiod actually do?
It stops the background service that manages every audio input and output on the Mac. macOS notices the service has stopped and starts a fresh copy within a second or two, which briefly interrupts any sound that was playing and then returns audio to normal.
Is it safe to run sudo killall coreaudiod?
Yes. It only restarts a background service, the same way quitting and reopening an app restarts that app. No settings, preferences, files, or paired devices are deleted. The only side effect is a fraction of a second of silence or a small click in whatever was playing.
Will restarting Core Audio fix a Bluetooth speaker that won't connect?
Sometimes, if the speaker is paired but stuck showing the wrong state in the Sound menu. It will not fix a speaker that has not been paired at all, is out of range, or is switched off, because those are not problems with the audio service.
Does restarting Core Audio delete my sound settings?
No, but any Multi-Output or Aggregate Device you had built in Audio MIDI Setup, and whichever output or input was selected at the time, is commonly cleared and needs reselecting once the service restarts.
What is the difference between restarting Core Audio and restarting my Mac?
Restarting Core Audio only restarts the audio service and takes a second or two, with no interruption to anything else running. Restarting the Mac reloads every system service, closes every app, and takes minutes. Try the audio-only restart first; if that does not help, a full restart is the next step.
