Mac Running Hot and Loud: Finding the Runaway Process

1 Sep 2026

A Mac that suddenly becomes hot, noisy and sluggish is often doing far more work than it should.

The fans may run at full speed, the keyboard or underside may feel unusually warm, battery life may drop quickly, and even simple tasks can become slow. On Apple silicon Macs, you may not always hear a fan, but the device can still become noticeably hot and reduce performance to protect itself.

In many cases, the cause is a runaway process: an application, browser tab, background task or system service consuming excessive processor power.

The quickest way to find it is with Activity Monitor.

What Is a Runaway Process?

A process is any application or background component currently running on the Mac.

Most processes use little processor power while idle. A runaway process behaves differently. It may become stuck in a loop, repeatedly retry a failed task or consume resources continuously.

Common causes include:

A frozen application
A browser tab running heavy scripts
Cloud storage repeatedly syncing the same files
Spotlight indexing
Photo analysis
Backup software
Antivirus or security scanning
A failed software update
Video rendering or media conversion
A printer or peripheral utility
A damaged application extension
Malware or unwanted software

High processor use is not automatically a fault. Video editing, gaming, software development and large file exports can legitimately make a Mac run hot.

The key question is whether the activity matches what you are actually doing.

First, Check the Mac’s Environment

Before blaming software, make sure the Mac can cool itself properly.

Avoid using it:

On a bed, sofa or blanket
Inside a closed cabinet
In direct sunlight
Beside a radiator
With vents obstructed
In an unusually hot room

Place the Mac on a hard, flat surface and disconnect unnecessary accessories.

For a MacBook, remove any case or cover that could be interfering with ventilation. Then wait a few minutes and see whether the temperature and fan noise improve.

If the Mac remains hot while apparently idle, investigate the running processes.

Open Activity Monitor

Open Finder and go to:

Applications > Utilities > Activity Monitor

You can also use Spotlight:

Command + Space

Type:

Activity Monitor

and press Return.

Activity Monitor shows the applications and background processes currently using the Mac’s resources.

The most useful tabs for heat and fan problems are:

CPU
Energy
Memory
Disk
Network

Start with CPU.

Sort Processes by CPU Usage

Select the CPU tab and click the % CPU column so the highest values appear at the top.

Look for a process using a large amount of processor power continuously.

Examples might include:

Safari

Google Chrome Helper

Microsoft Teams

OneDrive

Dropbox

photoanalysisd

mds

mdworker

WindowServer

kernel_task

The number can occasionally exceed 100% because Macs have multiple processor cores. A process using 200% is roughly consuming the equivalent of two full cores.

A short spike is normal. A process remaining near the top for several minutes deserves attention.

Identify the Application Behind the Process

Some process names are obvious. Others are not.

Select the process and click the information button in the Activity Monitor toolbar.

Review details such as:

Process name
Parent process
User
Open files and ports
Recent CPU usage
Application path

You can also double-click the process to see more information.

Do not force-quit an unfamiliar system process just because its name looks strange. First determine what created it and whether its activity is expected.

Check Whether the Process Is Responding

Activity Monitor may display:

Not Responding

beside a stuck application.

Try closing it normally first:

Switch to the application.
Save any work if possible.
Choose Quit from the application menu.

If it will not close, press:

Command + Option + Escape

Select the application and choose Force Quit.

You can also select it in Activity Monitor and click the stop button.

Force-quitting may cause unsaved work to be lost, so use it only when the application is clearly stuck or consuming excessive resources.

Watch the Process After Restarting the App

After closing the suspected application, wait a minute and check:

Whether CPU usage falls
Whether the fans slow down
Whether the Mac begins cooling
Whether performance improves

Then reopen the application.

If the same process immediately returns to high usage, the application may need:

An update
A restart
Its cache cleared
An extension disabled
A configuration change
A full reinstall

Repeatedly force-quitting the same process is not a permanent fix.

Browser Tabs Are Frequent Culprits

Web browsers can consume significant processor power, particularly when several tabs are open.

Common triggers include:

Video streaming
Animated adverts
Browser games
Video calls
Web-based dashboards
Social media feeds
Cryptocurrency scripts
Poorly coded websites
Browser extensions

Safari includes tools for identifying busy tabs, and Chromium-based browsers often show multiple helper processes in Activity Monitor.

Close tabs one at a time and observe whether CPU usage drops.

For Chrome and similar browsers, open the browser’s own task manager where available. This can show which tab or extension is responsible instead of presenting several generic helper processes.

Disable Browser Extensions Temporarily

Extensions can remain active across every tab and continue running in the background.

Temporarily disable extensions related to:

Ad blocking
Password management
Shopping
Screen recording
VPN services
Productivity tools
Tab management
AI assistants
Video downloading

Restart the browser and test again.

Re-enable extensions one at a time until the problem returns.

Remove extensions you no longer use or do not recognise.

Check the Energy Tab

For MacBooks, Activity Monitor’s Energy tab can be just as useful as CPU.

Look at:

Energy Impact
12 hr Power
Preventing Sleep
App Nap

An application may not be using extreme CPU at one exact moment but could still have a high energy impact over time.

This is particularly useful when the main symptom is:

Fast battery drain
Heat while the lid is open
Poor standby performance
The Mac refusing to sleep

Close or update applications with consistently high energy impact.

Spotlight Indexing Can Make a Mac Hot

After a macOS update, migration, external drive connection or large file change, Spotlight may rebuild its index.

Processes associated with indexing may include:

mds

mds_stores

mdworker

mdworker_shared

During indexing, the Mac may:

Run warm
Use more battery
Show sustained CPU activity
Access the disk heavily
Become temporarily slower

This normally settles once indexing finishes.

Do not repeatedly restart the Mac during legitimate indexing, as that can delay completion.

If indexing continues for an unusually long time or restarts constantly, a damaged index, problematic external drive or inaccessible folder may be involved.

Photos May Be Analysing the Library

The Photos app can perform background analysis for:

Faces
Objects
Memories
Search
Duplicate detection
iCloud Photos synchronisation

Relevant processes may include:

photoanalysisd

photolibraryd

mediaanalysisd

This activity is common after:

Importing a large photo library
Enabling iCloud Photos
Migrating to a new Mac
Updating macOS
Restoring from backup

Leave the Mac connected to power with Photos closed or idle and allow the analysis to complete.

If it never settles, check for damaged media files, stalled iCloud syncing or insufficient storage.

Cloud Sync Can Become Stuck

OneDrive, Dropbox, Google Drive and iCloud Drive can all create heat when repeatedly scanning or uploading files.

Warning signs include:

Constant sync icons
Repeated error messages
The same files appearing in the activity queue
High CPU and disk use
Large numbers of file changes
A sync client restarting itself

Open the sync application and look for errors.

Common causes include:

Unsupported filenames
Extremely large folders
Permission problems
Corrupt cache data
Files constantly being modified
Shortcuts pointing into synced folders
Two sync services monitoring the same location

Pause syncing temporarily and check whether CPU use and temperature fall.

Do not disconnect or delete a sync account until you have confirmed which files are stored locally and which exist only in the cloud.

Check for Backup Activity

Time Machine and third-party backup applications can use significant CPU, disk and network resources.

Processes may include:

backupd

or a vendor-specific service.

A backup may run heavily after:

A long period without connection to the backup disk
A large macOS update
Importing many files
Changing the photo or mail library
Replacing the backup destination

Open Time Machine settings or the relevant backup application and check whether a backup is active.

Allow a legitimate backup to finish where possible.

If the backup repeatedly fails and restarts, investigate the destination disk, network connection and available storage.

Look at Disk Activity

Select the Disk tab in Activity Monitor.

Sort by:

Bytes Written
Bytes Read
Reads in
Writes out

A process that constantly reads or writes large amounts of data can create heat even if its CPU usage is moderate.

Common examples include:

Cloud sync
Backup software
Search indexing
Virtual machines
Video editing
Database software
Antivirus scanning

Repeated disk activity may also indicate an application constantly regenerating cache files or logs.

Check Memory Pressure

Select the Memory tab and look at the Memory Pressure graph.

Green usually indicates healthy memory use. Yellow or red suggests the Mac is under pressure and may be using swap space heavily.

This can create:

Excess disk activity
Slow application switching
Heat
Beachballing
Loud fans
Reduced performance

Sort by the Memory column to find applications using the most RAM.

Browsers with many tabs, virtual machines, creative applications and development tools can consume large amounts of memory.

Close unnecessary applications and reduce the number of active tabs.

What Is

kernel_task

Many users see kernel_task at the top of Activity Monitor and assume it is the problem.

In reality, high kernel_task CPU usage is often a protective response to heat. macOS may make processor resources less available to other applications to reduce temperature and prevent further heating.

This means kernel_task is often a symptom rather than the original cause.

Look for:

Another process that was previously using heavy CPU
External devices producing heat
Blocked ventilation
Charging-related temperature
Hardware sensor problems
A demanding application

Do not attempt to delete, disable or modify kernel_task.

What Is WindowServer?

WindowServer is responsible for drawing and managing the visual interface.

Its usage can increase when:

Many windows are open
Several displays are connected
High-resolution external monitors are in use
Animated desktop effects are active
Applications constantly redraw their windows
Screen recording or sharing is running
Display scaling is demanding

Reduce the load by:

Closing unused windows
Disconnecting an external display temporarily
Stopping screen recording
Reducing visual clutter
Restarting applications with constantly changing interfaces
Logging out and back in

If WindowServer remains unusually high after all applications are closed, restart the Mac.

External Displays and Accessories Can Add Heat

High-resolution monitors, docks, capture devices and external storage can increase system activity.

Disconnect non-essential devices one at a time and monitor Activity Monitor.

Pay particular attention to:

USB-C docks
DisplayLink adapters
External GPUs on older Intel Macs
Audio interfaces
Capture cards
External hard drives
Network adapters

A faulty accessory or driver may cause repeated reconnections, background logging or high graphics activity.

Check Login Items

An application may begin consuming resources immediately after sign-in.

Open:

System Settings > General > Login Items & Extensions

Review:

Open at Login
Allow in the Background
Installed extensions

Disable non-essential items temporarily.

Restart the Mac and test again.

Do not disable security, backup or business-management tools without understanding their purpose.

Re-enable items gradually until the heat or CPU problem returns.

Restart the Mac Properly

A restart clears stuck processes and reloads system services.

Choose:

Apple menu > Restart

Avoid simply closing the lid or logging out.

After restarting, wait a few minutes before opening applications. Check Activity Monitor while the Mac is mostly idle.

If the runaway process returns before you open anything, it is likely a login item, background service, indexing task or system component.

Update the Problem Application

A runaway process may be caused by a known software bug.

Update the affected application through:

The App Store
The application’s built-in updater
The developer’s official website
Your organisation’s software-management system

Also check:

System Settings > General > Software Update

Install supported macOS updates after backing up important data.

Avoid downloading unofficial “fixed” versions or patches from unknown sources.

Reinstall the Application

If one application repeatedly causes high CPU use:

Back up its local data and settings.
Quit the application.
Remove it using the developer’s supported method.
Restart the Mac.
Install a current copy from a trusted source.
Test it before restoring optional extensions or settings.

Some applications install background helpers that remain after the main app is dragged to the Bin. Use the vendor’s uninstaller where one is provided.

Try Safe Mode

Safe Mode limits certain startup software, performs basic checks and clears some caches.

It can help determine whether the problem is caused by:

Third-party extensions
Login items
Caches
Background utilities
Additional drivers

The method for entering Safe Mode differs between Apple silicon and Intel Macs.

Apple silicon Mac

Shut down the Mac.
Press and hold the power button until startup options appear.
Select the startup disk.
Hold Shift.
Choose Continue in Safe Mode.

Intel Mac

Restart the Mac.
Hold Shift immediately during startup.
Release it when the login window appears.

Test the Mac in Safe Mode.

If the heat and CPU problem disappears, a third-party startup item or extension is more likely to be responsible.

Restart normally afterwards.

Check Storage Space

A nearly full drive can contribute to poor performance, excessive swapping and background maintenance activity.

Open:

System Settings > General > Storage

Make sure the Mac has a reasonable amount of free space.

Remove or move:

Large downloads
Old video exports
Unused installers
Duplicate backups
Virtual machine images
Unneeded applications

Avoid aggressive Mac-cleaning tools that remove unfamiliar files automatically.

Scan for Malware and Unwanted Software

Malware is less common than ordinary application faults, but it can cause persistent processor use.

Warning signs include:

Unknown processes returning after removal
Browser redirects
Unwanted extensions
Fake security alerts
Applications installed without permission
High network traffic while idle
Fans running constantly after startup

Use a trusted security product or your organisation’s approved endpoint protection.

Do not install multiple antivirus programs at the same time, as overlapping scanning can itself cause excessive CPU use.

Use Activity Monitor’s Sample Process Feature

For deeper investigation, select the suspicious process in Activity Monitor and choose:

Sample Process

This records what the process is doing during a short period.

The result is technical, but it may reveal:

A repeated function
A blocked file operation
A plugin or framework
A network component
A loop inside the application

Save the sample and provide it to the application developer or IT support team where appropriate.

Check Console for Repeating Errors

Open the Console application from:

Applications > Utilities > Console

Search for the suspicious process name.

A runaway process may be repeatedly recording the same error, such as:

Permission denied
File not found
Connection failed
Database locked
Extension crashed
Authentication failed

Constant logging can itself contribute to CPU and disk activity.

Console produces a large amount of information, so focus on repeated messages occurring at the same time as the heat problem.

Intel Mac or Apple Silicon: Does It Matter?

Both can experience runaway processes, but the symptoms may differ.

Intel Macs

Intel Macs often:

Produce more audible fan noise
Run hotter under sustained workloads
Reach thermal limits more quickly
Accumulate dust in cooling systems over time

Apple silicon Macs

Apple silicon Macs are generally more efficient, but they can still heat up during:

Video rendering
Gaming
Virtualisation
AI workloads
Large software builds
Multiple external displays
Heavy browser use

Fanless MacBook Air models cannot increase fan speed, so they may reduce performance sooner when they become hot.

When the Problem May Be Hardware

Software is not always responsible.

Possible hardware-related signs include:

Fans running at full speed immediately after startup
Heat while no applications are open
Sudden shutdowns
Battery swelling
Charging problems
Sensor errors
Fan grinding or rattling
Persistent high temperature in Safe Mode
A burning smell
Visible liquid damage

Stop using the Mac immediately if the battery appears swollen or the case is separating.

Back up important data and arrange professional inspection.

A Sensible Troubleshooting Order

When a Mac is hot and noisy, work through the problem in this order:

Place it on a hard, ventilated surface.
Disconnect unnecessary accessories.
Open Activity Monitor.
Sort the CPU tab by % CPU.
Identify any process using excessive resources.
Close the related application normally.
Force-quit it only if necessary.
Check browser tabs and extensions.
Review Energy, Disk and Memory activity.
Check Spotlight, Photos, backup and cloud-sync tasks.
Restart the Mac.
Disable non-essential login items.
Update or reinstall the offending application.
Test in Safe Mode.
Investigate hardware if the Mac stays hot while idle.

The most useful clue is not simply that the Mac is warm. It is which process is consuming resources at the time.

Need Help Finding What Is Making Your Mac Run Hot?

A runaway process can cause excessive heat, poor battery life, noisy fans and reduced performance. It may be caused by a browser, cloud-sync problem, software bug, background service or failing hardware.

Hamilton Group can analyse Activity Monitor, identify the process responsible and apply a reliable fix without unnecessarily wiping or replacing the Mac.

Call 0330 043 0069 or visit hgmssp.com to speak with one of our IT experts.