How to Fix High CPU Usage After Updating macOS

A macOS update can temporarily increase CPU usage while your Mac indexes files, analyzes photos, syncs data, or finishes other background tasks. High CPU usage can also come from an incompatible app, a login item, a browser tab, or a process that became stuck during the update.

Quick Answer

Open Activity Monitor and sort the CPU tab by % CPU to find the process using the most processor power. If it is a familiar app, quit or update that app. If it is a macOS process such as mds, mdworker, photoanalysisd, or cloudd, give your Mac time to finish its work, especially after a major update.

Then restart your Mac, install available app updates, reduce unnecessary login items, and check available storage. Do not force-quit unfamiliar system processes unless you know what they do. If high CPU usage continues for several hours or returns after every restart, use the troubleshooting steps below.

Why CPU Usage Rises After a macOS Update

CPU usage measures how much of your Mac’s processor is working. A brief increase is normal after updating because macOS may need to:

Rebuild Spotlight’s search index
Analyze photos and videos
Recreate caches
Sync iCloud Drive, Photos, Mail, or other services
Check and reorganize files
Update app data for the new system software
Reconnect external drives and accessories

These tasks can make the Mac feel warm, slow, or less responsive. They may also reduce battery life temporarily. The activity should normally decrease after the background work finishes.

High CPU usage is more concerning when it continues indefinitely, causes repeated freezes, makes fans run constantly, or is tied to one app that you are not using.

Check Which Process Is Using the CPU

Activity Monitor shows which apps and background services are using system resources.

Open Activity Monitor. You can find it in Applications > Utilities, or search for it with Spotlight.
Select the CPU tab.
Click the % CPU column heading so the highest values appear at the top. Click it again if the list is sorted in the opposite direction.
Watch the list for a minute or two. Note whether the same process remains at the top.
Select a process to view more information at the bottom of the window.

A process using a high percentage briefly is not necessarily a problem. CPU values can exceed 100 percent because Activity Monitor measures usage across multiple processor cores. Look for sustained usage and whether the process matches the symptoms you are seeing.

Common Processes After an Update

Some names commonly appear during post-update maintenance:

mds and mdworker: Spotlight indexing
photoanalysisd: Photo library analysis
cloudd: iCloud synchronization
kernel_task: macOS system activity and thermal management
launchservicesd: App and document registration
WindowServer: Drawing windows and user-interface elements

Do not delete system files or randomly terminate these processes. They may restart automatically, and repeatedly stopping them can interrupt important work.

Give macOS Time to Finish Background Work

If the top process is related to indexing, Photos, or iCloud, leave the Mac connected to power and connected to the internet. Keep it awake for a while so it can complete its tasks.

For a large drive or photo library, processing may take longer than expected. Avoid repeatedly restarting the Mac while indexing or synchronization is active because interruptions can extend the process.

You can check whether Spotlight is still indexing by selecting the Spotlight icon in the menu bar and searching for an indexing message. If the message disappears and CPU usage gradually falls, no further action may be necessary.

Restart Your Mac

A restart can clear temporary processes that became stuck during the update.

Save your work.
Close open apps if possible.
Choose Apple menu > Restart.
After the Mac starts, wait several minutes before opening demanding apps.
Check Activity Monitor again.

If the Mac is unresponsive, press and hold the power button only as a last resort. This can cause unsaved work to be lost.

Quit or Update the Problem App

If one third-party app consistently uses most of the CPU, quit it and check for an update. An app built for an earlier macOS release may need a compatibility update.

Save any work in the app.
Choose App Name > Quit App Name from the menu bar, or press Command-Q.
Reopen the app and test it.
Open the app’s built-in updater, or download the latest version from the developer’s official website.
If the app is installed through the App Store, open the App Store, select Updates, and install available updates.

Force Quit a Frozen App

Use force quit only when an app will not close normally. Any unsaved work in that app may be lost.

Press Option-Command-Escape.
Select the unresponsive app.
Click Force Quit.
Confirm the action if macOS asks.

Do not force-quit a process merely because its name looks unfamiliar. If the process is part of macOS, stopping it may cause other services to malfunction or restart.

Check Login Items and Background Activity

Apps that launch automatically can consume CPU immediately after startup. Removing unnecessary login items can prevent the problem from returning.

Choose Apple menu > System Settings.
Select General.
Click Login Items & Extensions.
Review the apps under Open at Login.
Select an app you do not need to start automatically and click the minus (-) button.
Review the background activity section and turn off permissions only for apps you recognize and no longer need running.

Removing an item from this list does not uninstall the app. It only changes whether the app or its helper opens automatically. If you do not recognize an item, search for its developer before disabling it.

Restart the Mac after making changes and check CPU usage again.

Install App and Accessory Updates

An outdated app, browser extension, printer utility, antivirus tool, VPN, or external-device driver can conflict with the updated system.

Check for updates in:

App Store: Open App Store, select Updates, and install available updates.
The developer’s official website for apps not installed through the App Store.
The manufacturer’s support page for printers, docks, displays, audio interfaces, and other accessories.
The settings or menu of security, VPN, backup, and synchronization tools.

Avoid downloading “Mac cleaner” utilities that promise to repair CPU usage automatically. They can add more background services and may remove files you still need.

Check Available Storage

macOS needs free storage for temporary files, caches, updates, indexing, and swap memory. Very low storage can make high CPU usage and sluggish performance worse.

Choose Apple menu > System Settings.
Select General.
Click Storage.
Review the recommendations and categories.
Remove only files and apps you recognize and no longer need.

Before deleting important files, make sure you have a current backup. Emptying the Trash permanently removes its contents. Large downloads, old installers, unused apps, and duplicate media often provide safer places to start than system folders.

Test in Safe Mode

Safe Mode starts macOS with limited software and performs additional checks. It can help determine whether a login item, extension, or third-party service is causing the high CPU usage.

First, shut down the Mac. The startup procedure depends on whether it has an Apple silicon chip or an Intel processor.

Apple silicon Mac

Choose Apple menu > Shut Down.
Wait until the Mac is fully off.
Press and hold the power button until Loading startup options appears.
Select a volume.
Press and hold the Shift key, then click Continue in Safe Mode.
Sign in when prompted.

Intel-based Mac

Choose Apple menu > Shut Down.
Turn on the Mac.
Immediately press and hold the Shift key.
Release the key when the login window appears.
Sign in.

You may need to sign in twice, and the login window may show Safe Boot in the menu bar. Check Activity Monitor in Safe Mode.

If CPU usage is much lower in Safe Mode, a login item, extension, security tool, or other third-party software is a likely cause. Restart normally, then remove or update recently installed software one item at a time.

Safe Mode is a diagnostic environment, not a permanent performance mode. Some features and apps may not work normally while it is active.

Reset a Stuck Spotlight Index

If mds or mdworker remains busy for an unusually long time, Spotlight’s index may need to be rebuilt. The graphical method is safer for most users.

Choose Apple menu > System Settings.
Select Siri & Spotlight.
Click Spotlight Privacy.
Add your internal drive or a folder to the privacy list.
Wait a few seconds.
Select the drive or folder in the list and click the minus (-) button to remove it.

Removing the location from the privacy list allows Spotlight to index it again. The Mac may use significant CPU while rebuilding the index. Do not exclude your entire internal drive permanently unless you understand that Spotlight searches will no longer include it.

Use Terminal to Rebuild Spotlight Only When Necessary

Terminal provides another method, but it changes Spotlight’s indexing state. Use it only if you are comfortable entering commands exactly as shown.

Before proceeding, save your work. The command may start a lengthy indexing process that uses CPU and storage activity.

sudo mdutil -E /

This erases and rebuilds the Spotlight index for the startup volume. Terminal will ask for your administrator password. The cursor may not move while you type; this is normal. Press Return when finished.

To check the indexing status, use:

mdutil -s /

To stop indexing on the startup volume, use:

sudo mdutil -i off /

This is a diagnostic or temporary measure, not usually a recommended permanent setting because Spotlight search will be limited. To reverse it and allow indexing again, use:

sudo mdutil -i on /

Let the rebuild finish before judging performance. Reindexing can temporarily increase CPU usage.

Troubleshooting Persistent High CPU Usage

CPU usage is high only when a browser is open

Quit unused tabs and windows, disable recently installed extensions, and update the browser. A single page with video, interactive content, or a faulty script can use substantial CPU. Test with a private window to determine whether extensions are involved.

`kernel_task` is using a lot of CPU

kernel_task is part of macOS. High usage can occur when the Mac is warm or when the system is managing temperature. Check whether vents are blocked, move the Mac to a hard surface, disconnect unnecessary accessories, and allow it to cool.

Do not try to disable or delete kernel_task. That can interfere with system protection and thermal management.

CPU usage returns after every restart

Check General > Login Items & Extensions, then temporarily remove recently installed utilities, antivirus tools, VPN clients, backup tools, and device software. Reinstall or update them only after confirming which one is responsible.

The Mac is slow but CPU usage is not high

CPU may not be the limiting resource. In Activity Monitor, check the Memory tab for memory pressure and the Disk tab for heavy disk activity. Low storage, a failing drive, or extensive synchronization can cause slowness without a high CPU reading.

The Mac freezes or restarts unexpectedly

Back up important files first. Disconnect nonessential accessories and test again. If the problem continues, contact Apple Support or an Apple Authorized Service Provider. Bring the name of the process shown in Activity Monitor and note when the problem started.

Frequently Asked Questions

How long should high CPU usage last after a macOS update?

There is no fixed time. It depends on the size of the update, your storage, photo library, and synchronization workload. CPU usage should gradually decline once indexing and other maintenance tasks finish.

Is it safe to force-quit a process using 100 percent CPU?

Not always. Force-quit only an app you recognize and that has stopped responding. Avoid terminating core macOS processes unless reliable troubleshooting instructions specifically call for it.

Will restarting stop macOS from indexing?

A restart may interrupt indexing, but macOS can resume it later. Repeatedly restarting usually does not solve the underlying cause and may delay completion.

Should I delete caches to fix high CPU usage?

Usually not. macOS and apps manage caches automatically, and deleting them can cause apps to rebuild data or lose temporary settings. Identify the process causing the usage before removing files.

Can high CPU usage damage my Mac?

Modern Macs are designed to manage heat and reduce performance when necessary. However, constant heat, unexpected shutdowns, loud fans, or repeated crashes should be investigated rather than ignored.

Final Thoughts

High CPU usage after a macOS update is often temporary, especially when Spotlight, Photos, or iCloud is completing background work. Use Activity Monitor to identify the actual cause, allow system maintenance to finish, and then address persistent problems by updating apps, removing unnecessary login items, checking storage, and testing in Safe Mode. If the issue continues with freezing, crashes, or overheating, back up your Mac and seek Apple support.