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Why is my Mac fan so loud? How to find the app and check CPU temperature

A loud fan is your Mac telling you something is working the CPU hard. Here's how to find out what, check how hot it's running, and make it quiet again, using tools already on your Mac.

By the NotchDodo teamUpdated 7 min read
See the culprit in your notchNotchDodo, $4.99 one-time
The short answerYour Mac's fan gets loud when something keeps the CPU busy: an app or browser tab stuck in a loop, Spotlight indexing after an update, an export or a build. To find it, open Activity Monitor, click CPU and sort by % CPU. The app at the top is the cause. Quit it and the fan settles within a minute or two. macOS has no built-in way to see CPU temperature in degrees on Apple silicon; an app like NotchDodo shows it, with fan speed and the busiest app, in your notch.

Why your Mac fan gets loud

Fans spin faster to move more air when the chip heats up, and the chip heats up when it's busy. Apple calls the rushing sound "a normal part of the cooling process" during heavy work. The usual reasons, roughly in order of how often we see them:

  • A runaway app. A browser tab running a heavy script, a stuck helper process or an app in a loop can hold a full CPU core for hours.
  • Heavy work you started. Exporting video, compiling code, running a local AI model or a game. Loud is expected here.
  • Spotlight indexing. After a macOS update or moving to a new Mac, mds_stores and mdworker index your files for a while.
  • Too many browser tabs. Each tab is its own process, so dozens of them add up to a lot of CPU and memory.
  • Heat around the Mac. A soft surface like a bed or a lap blocks the vents, and a hot room means less cooling headroom.

If kernel_task shows up at the top, it isn't the culprit. According to Apple, it helps manage CPU temperature by making the CPU less available to the processes using it heavily. It's a symptom: find the app below it.

Method 1: find the app in Activity Monitor

Activity Monitor is built into every Mac and is the quickest way to see what's working your CPU.

  1. Press Command-Space, type Activity Monitor and press Return. It also lives in Applications → Utilities.
  2. Click the CPU tab.
  3. Click the % CPU column header so the busiest process is at the top. Click again if the arrow points the wrong way.
  4. Watch it for 10 to 20 seconds. Something that stays near the top is your cause; a brief spike usually isn't.
  5. To quit it, select the process, click the X button in the toolbar and choose Quit. Use Force Quit only if it ignores you.
Why is it over 100%? % CPU counts each core as 100%, so a process at 140% is keeping more than one core busy. Browsers and apps also spread work across helper processes, so add up everything named after the same app (for example "Google Chrome Helper") to see its real total.

Also check the Memory tab sorted by Memory. An app that keeps growing makes macOS compress and swap memory, which is more work for the CPU and more heat. For a running graph, choose Window → CPU History. Apple's Activity Monitor guide explains every column.

Method 2: find it from Terminal

If you live in Terminal, top sorted by CPU gives the same answer. Press q to exit:

Terminal
top -o cpu -n 10

For a one-off snapshot you can paste into a chat or a bug report, take two samples (the first one has no CPU rate yet) and keep the second:

Terminal
top -l 2 -o cpu -n 10 -stats pid,command,cpu,mem | tail -11

Or with ps, sorted by CPU, with memory in kilobytes:

Terminal
ps -Aco pid,pcpu,rss,comm -r | head -11

To stop a process from Terminal, use its PID with kill <PID>, which asks it to quit politely. Save kill -9 for processes that ignore that.

How to check CPU temperature and fan speed

Here's the catch: macOS has no built-in app that shows CPU temperature in degrees, and Activity Monitor doesn't show temperature or fan speed at all. What you can get depends on your Mac.

Apple silicon (M1 and later)

The built-in powermetrics tool doesn't report degrees on Apple silicon. It reports the thermal pressure level instead, such as Nominal, which tells you whether macOS has started slowing the chip to cool it:

Terminal (asks for your password)
sudo powermetrics --samplers thermal -n 1 -i 1000

Intel Macs

On Intel Macs, the SMC sampler prints the CPU die temperature and fan speed directly:

Terminal, Intel Macs only
sudo powermetrics --samplers smc -n 1 -i 1000

What counts as normal

Apple doesn't publish a target CPU temperature, and the chip manages itself. On the M5 MacBook Pro we tested, the hottest CPU core read about 40 to 50°C at idle with the fan stopped. Under sustained heavy load, Apple silicon can run in the 90s °C; that's by design, and macOS slows the chip before it gets unsafe. What you control is the room: Apple says to use Mac laptops where the ambient temperature is between 10°C and 35°C.

Fan speed works the same way. On Apple silicon MacBook Pros the fans stop completely when the chip is cool, so silence at idle is normal, and they ramp up gradually under load. MacBook Air models with Apple silicon have no fan at all.

Method 3: see it in your MacBook notch

Activity Monitor answers the question once you go looking. The annoying part is that the fan usually kicks in while you're doing something else. NotchDodo turns the MacBook notch into a small dashboard, and its System Stats tool keeps an eye on this for you.

Runaway app alerts

If an app holds a full CPU core for five minutes, keeps growing in memory, or uses more than 40% of your RAM, the notch shows its icon and the number. It only flags the same app again if things get worse, so a big browser that stays big won't nag you.

The MacBook notch showing the Xcode icon with a red badge on the left and 142% in red on the right
A runaway app alert in the notch: which app, and how much CPU. Demo data.

Top apps, temperature and fan speed in one panel

Open the notch on System Stats and you get the three apps using the most CPU or memory (one number per app, helpers included) with a Quit button, plus the hottest CPU core in °C and the fan speed beside the CPU gauge. When the fan is resting it says "Fan off".

NotchDodo System Stats panel with CPU temperature 54°C, fan speed 3,120 rpm, and Top apps with Xcode flagged at 142%
System Stats: temperature and fan speed on the CPU tile, Top apps with a flagged app and its Quit button. Demo data.
36 seconds: from a loud fan to the app behind it, in the notch.

Everything is read on your Mac; nothing is uploaded. Alerts check quietly every 10 seconds and can be turned off in Settings. NotchDodo only reads the fan, it never changes its speed. The same notch also shows your calendar, a Pomodoro timer, clipboard history and Claude Code usage.

How to quiet the fan once you've found the cause

  • An app or tab you don't need right now: quit it. In a browser, the browser's own task manager (Chrome: Window → Task Manager) shows which tab is heavy.
  • Spotlight indexing: let it finish; it's a one-time job after an update or migration. Leaving the Mac plugged in and awake helps.
  • Work you started: loud is normal during an export or build. It settles a minute or two after the job ends.
  • Vents blocked: use the Mac on a hard, flat surface such as a desk, as Apple recommends, not a bed or cushion.
  • Still loud with nothing busy: on Apple silicon laptops Apple suggests closing and opening the lid or restarting. If the fan stays loud at idle after that, contact Apple Support.

Which method should you use?

Activity MonitorTerminalNotchDodo
Finds the busy appYesYesYes, and alerts you
Groups helpers per appNoNoYes
CPU temperature in °CNoIntel onlyYes
Fan speedNoIntel onlyYes
Tells you without lookingNoNoYes, in the notch
Quit from the same viewYesWith killYes
CostFree, built inFree, built in$4.99 one-time

For a one-time mystery, Activity Monitor is all you need. If it keeps happening, or you want to see temperature and fan speed on an Apple silicon Mac, having the answer waiting in the notch saves you the hunt every time.

Know why your fan kicked in, at a glance.NotchDodo shows runaway apps, top apps, CPU temperature and fan speed in your MacBook notch, with 17 more tools. One-time purchase, no subscription.Get NotchDodo for $4.99See all 18 tools

Sources

Mac, MacBook and Activity Monitor are trademarks of Apple Inc. NotchDodo is an independent app and is not affiliated with Apple.

Frequently asked questions

Why is my MacBook fan so loud all of a sudden?

Almost always because something is keeping the CPU busy: an app or browser tab stuck in a loop, Spotlight indexing after an update or a migration, a video export or build, or a backup. Open Activity Monitor, click CPU, sort by % CPU, and the app at the top is your answer. Using the Mac on a soft surface that blocks the vents makes it worse.

How do I check my CPU temperature on a Mac?

macOS doesn't show CPU temperature in degrees in any built-in app. On Apple silicon, sudo powermetrics --samplers thermal shows the thermal pressure level (for example Nominal), not degrees. On Intel Macs, sudo powermetrics --samplers smc prints the CPU die temperature and fan speed. To see degrees on Apple silicon you need an app that reads the Mac's sensors, such as NotchDodo, which shows the hottest CPU core and fan speed in the notch.

What is a normal CPU temperature for a Mac?

There's no single number, and Apple doesn't publish one. Idle Macs usually sit well below 60°C; on the MacBook Pro we tested, the hottest core read about 40 to 50°C at idle with the fan off. Under sustained heavy load, Apple silicon chips can run in the 90s °C, and that's by design: macOS slows the chip and spins up the fans to keep it in a safe range. What matters is the room you use it in: Apple recommends an ambient temperature between 10°C and 35°C.

Why is kernel_task using so much CPU?

kernel_task is part of macOS. One of its jobs is managing CPU temperature: when the chip gets hot, it makes the CPU less available to the processes using it heavily, so it appears to use a lot of CPU and you hear the fans. It isn't the cause. Find the app that's working the CPU hard, quit it, and kernel_task calms down on its own.

Why does my Mac's fan sometimes stop completely?

Fans on Apple silicon Macs turn off entirely when the chip is cool, so a silent fan at idle is normal. MacBook Air models with Apple silicon have no fan at all and cool passively, slowing the chip down a little under long heavy loads instead.

Should I force quit an app that's using 100% CPU?

Try a normal Quit first so the app can save your work. In Activity Monitor, select the process, click the X button in the toolbar and choose Quit. Use Force Quit only if it doesn't respond. Don't quit system processes such as WindowServer or kernel_task.

Can I control my Mac's fan speed?

macOS manages fan speed automatically and doesn't offer a setting for it. Third-party fan control apps need a privileged helper to write to the Mac's controller. NotchDodo only reads fan speed, it never changes it.

Does NotchDodo send my system data anywhere?

No. CPU, memory, temperature and fan readings are read on your Mac and never leave it. Runaway app alerts check every 10 seconds in the background and can be turned off in Settings.