Safe to Quitcoreduetd on Mac: what the Duet daemon does and why it is at 100 percent
coreduetd is the CoreDuet daemon. It keeps a small database of how and when you use apps, devices and places, and other parts of macOS use that to predict what you will do next: Siri Suggestions, the Handoff icon in the Dock, which background jobs to run and when. It is normally near zero. After a macOS update, a migration or a long time off, it rebuilds its database and can sit at 100 percent of one core for a while, then settles. Do not quit it; it relaunches within a minute. If it is still pinned a day later, the steps below cover it.
- What it is
- Apple's activity and usage model. It records app, device and location patterns so macOS can predict and schedule. Runs from /usr/libexec/coreduetd.
- Normal
- 0 to 1 percent CPU most of the day, a burst of 50 to 100 percent of one core for minutes to an hour after an update or migration.
- Not normal
- 100 percent of one core for more than a day on a Mac that has not changed, especially with the fan on and nothing else busy.
- Safe to quit?
- No. Force quit works for about a minute, then it is back. One Apple Community poster put it exactly that way.
- The one safe fix
- Give it a day on power. If it is still pinned, turn Handoff off and on in System Settings, then restart.
What coreduetd does
coreduetd has been in every version of macOS since Yosemite, running from /usr/libexec/coreduetd with the bundle identifier com.apple.coreduetd.osx. CoreDuet is Apple's framework for understanding how a device is used. The daemon keeps a local database (never sent to Apple as a whole) of events: which apps you open and when, which devices are nearby, where the Mac is, when it is on power, when you tend to sleep it. Other parts of the system ask it questions: "Is this user likely to open Mail in the next ten minutes?" or "Is now a good time to run a heavy background job?"
That is why so many unrelated features depend on it. Siri Suggestions in Spotlight and Safari draw on it. The Handoff icon that appears in the Dock when your iPhone has a page open goes through it. The Duet Activity Scheduler, dasd, asks it when the user is idle before launching backups, photo analysis and updates. Low Power Mode and battery predictions use its idea of your daily pattern.
When the database is in good shape, answering those questions is instant. When it has to be rebuilt or compacted, coreduetd grinds through weeks of events, and that is the burst people see in Activity Monitor.
What normal looks like
coreduetd has two modes: quiet bookkeeping, and the occasional rebuild. The rebuild is the one that gets noticed:
Note the "one core" part. coreduetd is mostly single threaded, so on an 8 or 10 core Mac a reading of 100 percent in Activity Monitor is one core fully busy, not the whole machine. The Mac stays usable; the cost is heat and battery.
Why coreduetd is using CPU right now
Working through the threads where people solved it, the causes come down to:
- A recent update. Catalina, Big Sur, Monterey and Ventura each produced a wave of "coreduetd at 100 percent" threads in the week after release. The database is being reprocessed. Wait a day.
- A migration from another Mac. Migration Assistant brings the old usage history with it, and coreduetd has to index all of it.
- A Handoff or Continuity loop. An Apple Community poster in December 2022 found it "has something to do with Handoff" and turning Handoff off calmed it. Two devices on the same Apple ID that keep advertising activities to each other can keep coreduetd busy indefinitely.
- A corrupt database. If an update was interrupted or the disk filled up mid-write, the database in /var/db/CoreDuet can be damaged, and coreduetd retries forever. This is the case that needs a restart or, in the worst case, Apple support.
- Low disk space. coreduetd compacts its database regularly. With almost no free space the compaction fails and repeats. Free up space and it finishes.
What it is not: spyware, and not something that sends your activity to Apple. The data stays on the Mac and is used by the Mac. It is also not something a cleaner app can fix.
Is it safe to quit coreduetd?
Not usefully. coreduetd is a system daemon kept alive by launchd. You can force quit it from Activity Monitor and nothing breaks, but as the poster of a 2022 Apple Community thread wrote, "You can force quit it but it pops back on in a minute." It resumes exactly the job it was doing, so the CPU returns too.
You will find older advice online to delete the CoreDuet database folder or to unload the daemon with Terminal commands. Skip both. The folder is protected on modern macOS, unloading is blocked by System Integrity Protection, and even where those steps worked they only forced the same rebuild you were trying to avoid. The safe levers are time, the Handoff switch, free disk space and a restart.
Type any process name above to see whether it is one that settles, one you can quit, or one to leave alone. coreduetd is firmly in the "leave and wait" group.
What to do, in order
- Check what changed in the last day
A macOS update, a migration, a new Mac, or a long time switched off. If any of those apply, coreduetd is rebuilding its model. Plug in, leave the Mac awake for a few hours, and check again tomorrow.
- Free up disk space
If the startup disk has less than 10 GB free, coreduetd's housekeeping can fail and repeat. Empty the Trash, clear Downloads, and see our free up space page. Then give it an hour.
- Turn Handoff off and on
Open System Settings, General, AirDrop & Handoff. Turn off Allow Handoff between this Mac and your iCloud devices, wait a minute and watch coreduetd. If it drops, turn Handoff back on; if it climbs again, leave it off for a day and then retry. Also check your iPhone and iPad are up to date, since the loop is between devices.
- Restart the Mac
A restart closes the database cleanly and lets coreduetd reopen it. If it has been pinned for more than a day, do this now rather than waiting longer.
- Try safe mode once
Start in safe mode (hold Shift at login on Intel, or hold the power button and choose the disk with Shift held on Apple silicon), log in, wait ten minutes, then restart normally. Safe mode runs a disk check and clears caches, which fixes the stuck-database case for most people. If it is still pinned after this, contact Apple support; a reinstall over the top of macOS is the next step and it keeps your files.
When to worry
The only costs are heat, fan noise and battery. coreduetd cannot damage your data. The deciding factor is how long it has been pinned relative to what changed:
- First hourAfter an update: normal rebuild. Do nothing.
- First dayAfter a migration or a new Mac: still normal. Keep it on power and awake.
- Day 2Pinned with nothing new. Free space, toggle Handoff, restart.
- Day 3 and beyondStill 100 percent of a core after a restart and safe mode. Stuck database. Apple support or a reinstall over the top.
The difference between a long rebuild and a loop is whether the work is ending, which is hard to tell from one look at Activity Monitor. Safe to Quit tracks each process over hours and shows whether it fell back, so you know on day one whether to wait or act.
What people hit, in their words
“But it takes up 100% of my MacBook's server power and is making my computer super sluggish.”
“You can force quit it but it pops back on in a minute.”
“I found out that it has something to do with Handoff, so I have disabled handoff”
Questions people ask
What is CoreDuet?
CoreDuet is Apple's framework for modeling how a device is used: which apps you open, when, where, which devices are nearby and when the Mac is idle. Its daemon, coreduetd, keeps that model in a local database on the Mac. Siri Suggestions, Handoff, the background task scheduler and battery predictions all ask it questions. The data is used on the device to make predictions, not uploaded as a whole.
Why is coreduetd using 100 percent CPU?
Usually because it is rebuilding or compacting its usage database after a macOS update, a migration from another Mac, or a long time off. That takes minutes to hours and ends on its own. If it stays pinned for more than a day, the common causes are a Handoff loop between your Apple devices, very low disk space, or a damaged database. Toggle Handoff, free space, and restart.
Can I disable coreduetd?
Not on a modern Mac. It is protected by System Integrity Protection and relaunched by launchd within a minute of being force quit. Disabling it on older systems also broke Siri Suggestions, Handoff and parts of background scheduling. Rather than trying to remove it, give it time to finish, then use the Handoff toggle and a restart if it is genuinely stuck.
Why is my CPU load so high on my Mac?
Open Activity Monitor, click the CPU tab and sort by % CPU to see which process is responsible. A system process like coreduetd, mds_stores or photoanalysisd at the top after an update is normal background work that settles within hours. An app at the top that you are not using is a stuck app; quit it. kernel_task at the top usually means the Mac is hot and throttling itself.
What is Core Sync on a Mac?
Core Sync is not related to coreduetd. It is Adobe's background sync process, installed with Creative Cloud, which keeps Creative Cloud files and fonts in sync. If Core Sync is using CPU, the fix is in the Creative Cloud app: pause file syncing, sign out and in, or update it. coreduetd, by contrast, is Apple's and is on every Mac whether or not Adobe software is installed.
Sources and further reading
- What is coreduetd? Ask Different, Sep 2017. Path, bundle identifier and a description of the CoreDuet framework.
- coreduetd is crippling my mac; what does Apple advise? Apple Community, Apr 2022. Source of two quotes above.
- Coreduetd using 100% of one CPU core at all times Apple Community, Dec 2022. The Handoff finding.
- Use Handoff to continue tasks on your other Apple devices Apple Support. Where the Handoff setting lives and what it requires.
- dasd on Mac Our page on the scheduler that asks coreduetd when to run background jobs.