What is coreaudiod on a Mac, and why is it using CPU?

coreaudiod is the macOS process that plays and records all the sound on your Mac. Every app that makes a noise or listens to a microphone goes through it, so it is busy whenever audio is busy: a call, a music app, a recording, a game. Some processor use while sound is playing is normal. It becomes worth a look when it stays high with nothing playing, or when the sound itself crackles or cuts out.

This post covers what coreaudiod does, why it climbs, how to find the app behind it, and how to restart audio with the least damage.

What coreaudiod does

Apps do not talk to your speakers, headphones or microphone directly. They hand their sound to coreaudiod, which mixes everything together, converts it to the format each device wants, and sends it out. It does the same in the other direction for anything you record or any call you are on. It also keeps track of the devices that come and go: AirPods connecting, a USB microphone being plugged in, a display with speakers being attached.

That is why it is a single process for the whole Mac, and why it is always running. Foreman, which knows macOS’s process names, lists it as “Core Audio” and describes it as “Plays and records all sound on the Mac.”

Why coreaudiod uses CPU

Some of these are expected, and some point at a problem.

• Calls and meetings. A video call has your microphone, your speakers and often a second device all running together, and coreaudiod has to carry all of it in step. Conferencing apps are among the busiest users of audio.
• Music and audio production apps. An app that runs effects, many tracks or software instruments sends a lot of audio through the system. Most of that work happens inside the app itself, but coreaudiod carries the result.
• Many devices at once. Bluetooth headphones, a USB interface, an HDMI display and the built-in speakers can all be present. Each one gives coreaudiod something to manage.
• An app that keeps the audio open. Some apps leave their audio running after the music stops, so coreaudiod keeps working for sound that is silent. A browser tab that once played a video can be one.
• A stuck audio device. After an unplugged cable, a sleeping Mac or a Bluetooth device that connected badly, coreaudiod can end up in a state where it spends processor time and the sound is broken as well.

The last case is the one people notice, because the symptoms are loud: crackling, delays, no sound at all, or a headset that connects but stays silent.

Find the app behind it

Before restarting anything, check what is feeding it.

1. Look at what is playing. A browser tab with a speaker symbol, a music app and a call app are all candidates. Pause or quit them one at a time and watch whether coreaudiod calms down.
2. Check what is listening. When an app is using the microphone, macOS shows an indicator for it in the menu bar, and Control Center names the app. An app you forgot about may be holding it.
3. Check the devices. In System Settings, open Sound, and look at the Output and Input tabs. If a device you are not using is selected, switch to the right one.
4. Close the browser tabs that played sound. If you cannot tell which tab it is, how to tell if one browser tab is slowing down your Mac shows how to work it out.

A process list helps with step 1. In Foreman’s Processes page, sort by CPU and read the rows near the top, and open the one for your browser or call app to see its helpers added up. If coreaudiod is high while the app above it is also high, the app is the cause and coreaudiod is just carrying its load. If an app you want to keep open is only working in the background, Efficiency Mode may help, and Foreman runs an app at full speed in front or while it plays sound, so a music app is not held back while it plays. Efficiency Mode is not offered for coreaudiod itself: it runs under a system account, _coreaudiod, and macOS only lets an administrator slow those down. See how Foreman’s Efficiency Mode works and when to use it.

How to restart audio with care

If sound is broken and nothing else explains it, restarting coreaudiod is a known fix. You do not need to start it again yourself: launchd brings it back as soon as anything on the Mac asks for sound, which is usually within a moment.

Expect three things when you do it. Any sound that is playing stops. An app in the middle of a call or a recording may lose its audio, and some apps need to be restarted to find the sound again. Nothing is deleted, and nothing you have saved is touched.

So, save your work, stop recordings and finish the call first. Then there are two ways.

1. The gentle way. Quit the app that was using sound, switch the output in System Settings > Sound to another device and back, then open the app again. This often clears a stuck device without touching coreaudiod.
2. The direct way. In Terminal, run:

sudo killall coreaudiod

It asks for your password, and your account needs to be an administrator. The sound drops for a moment, and macOS starts coreaudiod again the next time an app asks for sound.

In Foreman, the cleaner way is the Services page: find com.apple.audio.coreaudiod and choose Restart. It is a system service, so Foreman asks for an administrator password first. Treat it as a repair, not a habit. If you have to do it every day, something else is wrong: a device, a cable, an app, or a macOS update that has not been installed.

If a restart of the whole Mac clears it and it then comes back, the cause is usually one particular app or one particular device. Work back through the list above, one at a time.

When to worry

coreaudiod is a normal part of macOS, and the process itself is not a sign of anything unusual. These signs deserve attention.

• It stays high for minutes with no sound playing and no call open, and quitting apps does not change it.
• Sound crackles or drops even when the Mac is not busy.
• The Mac gets warm or the fans run while nothing audible is happening. What to do when your Mac fans get loud covers the next steps.

If none of these apply, leave it alone. A process that carries all the sound on a computer is allowed to work.

The short version

coreaudiod is macOS’s sound server: it plays and records everything. It is busy when audio is, and it is safe to restart when sound is broken, as macOS brings it back by itself. Look for an app or device holding audio open before blaming it, and save your calls and recordings first. If you would like a plain list of what each process is doing, Foreman names about 120 macOS processes in plain English, coreaudiod among them, and it is free for 24 hours.