Why your MacBook gets hot, and how to find what's heating it

A MacBook gets hot because something is making the processor or graphics chip work hard for a long time. Heat is a side effect of work, so the fix is to find what is doing the work: an app stuck in a loop, a browser tab running video or a game, or a background job such as indexing. Warm for a few minutes while you export a video is normal. Hot and noisy while you are only reading email is a sign that an app needs a closer look.

This post walks through how to tell the two apart, how to find the app responsible, and what else changes how hot a laptop gets.

What heat actually means

Every chip turns the electricity it uses into heat. The more work it does, the more heat it gives off, and a laptop has to lose that heat through a very thin case. A MacBook Pro has fans to move the heat out. MacBook Air models with Apple silicon have no fan at all, so they stay silent and the case simply gets warm.

Two kinds of work cause most of the heat people notice:

• Sustained processor work. One app asking for a lot of processor time, minute after minute. Video export, a photo library being analysed, a web page with a runaway script, or a build in a developer tool.
• Graphics work. Games, video calls with effects, 3D tools, and screen recording all use the graphics chip, and on Apple silicon Macs the processor and graphics share one chip, so they share one heat budget.

Short bursts do not matter much. Opening an app or loading a page spikes the processor for a second and it settles. What matters is whether the heat keeps going after you have stopped asking for anything.

Is it normal or is it a problem?

A few questions sort most cases quickly.

1. What were you doing? Exporting video, playing a game, running a video call with a shared screen, or compiling code will warm any Mac. If the heat starts when the job starts and fades when it ends, nothing is wrong.
2. Is it hot while idle? If the Mac feels hot with only a document or an email open, something is running that you did not start.
3. Is it plugged in? Charging adds heat of its own. A Mac that is charging and also working hard can run warmer than one doing the same work on battery.
4. Did it start recently? Heat that began after a macOS update is often catch-up work, such as Spotlight re-indexing your files, which finishes by itself. Why is my Mac slow after a macOS update? covers that case.

If the answer to the second question is yes, move on to finding the app.

Find the app that is heating it

The macOS Force Quit window (Option-Command-Escape) lists your open apps, but it does not show how much processor any of them is using, so it cannot tell you which one is hot. You need something that shows live figures per app.

Foreman does that. Open it from anywhere with Control-Shift-Escape and look at the Processes page. It splits what is running into Apps, Background processes and System processes, and each row has a CPU column and a GPU column. Click the CPU column header to sort, and the app at the top is the one using the most processor time right now. Click GPU to sort by graphics use instead. Each app’s figure is a share of the whole Mac, and the Mac’s total sits above each column, so you can see whether one app accounts for most of it.

Two details help here:

• Helpers are added up under their app. A browser runs many helper processes. Foreman groups them under the browser’s row, so you see the browser’s real total and can open the row to see which helper is the busy one.
• Look for a pattern, not a spike. Watch for 20 to 30 seconds. An app that sits near the top the whole time is your candidate. How to see which app is using the most CPU on a Mac goes into reading those figures.

The Performance page adds a large live graph for CPU and one for GPU, and below each graph, the apps using the most. If the CPU graph is flat and the GPU graph is high, the heat is coming from graphics, and you should look at the apps listed under GPU.

Foreman does not show temperatures or fan speeds. It shows what is working, which is the cause of the heat, not the heat itself.

What to do once you have found it

Match the response to the app.

• An app you are using, doing a real job. Let it finish. A heavy job is a fair reason for a warm Mac.
• An app you are not using right now. Quit it. In Foreman, select it and press End Task, which asks the app to quit the normal way so it can offer to save your work.
• An app you need open but not right now, such as a chat client or a sync app: turn on Efficiency Mode for it. In the background the app then runs at background priority and in short bursts, held to about a quarter of the processor time it would otherwise take. In front, or while it plays sound, it runs at full speed. The setting is remembered for that app.
• A browser tab. Find the helper that is busy, close tabs you do not need. The same sorting trick works for finding the busy tab’s helper.
• A stuck app that sits at a high figure and does nothing useful: quit it, and if it will not quit, force quit it. You lose unsaved changes in that case, so try the normal quit first.

How much a change helps depends on how busy the Mac is. Do not expect a fixed drop. Watch the figures for a minute afterwards and see.

The kernel_task process and a Mac that slows itself down

Sometimes the busiest thing on the list is not an app but a process named kernel_task. It is the core of macOS, and it can show a lot of CPU use even when you are doing nothing heavy.

A high kernel_task figure often means the Mac is slowing itself down to stay cool. kernel_task takes up processor time so that less is left for the apps working it hardest, which lowers the heat. So when you see it high, the Mac is not broken. It is protecting itself, and the cause is whatever made it warm in the first place: find that app using the steps above. Foreman never offers to end kernel_task, and you cannot sensibly end it anyway. What is kernel_task on a Mac and why does it use so much CPU has the full story, and why a Mac slows down when it gets warm explains the slowing.

Things around the Mac that add heat

Not all heat is software. Check these before you blame an app.

• Soft surfaces. A bed, a sofa or a pillow blocks the vents and traps heat. A desk or a hard tray works better.
• Direct sun and warm rooms. A Mac in a hot car or in sun on a table starts with less room to cool.
• Blocked vents. On a MacBook with fans, keep its vents clear of anything soft or pressed against them. Dust can build up inside over years, and a repair shop can clean it.
• Lots of external displays. More screens mean more graphics work.
• Charging while you work hard. If you can, let a heavy job run when the battery is already full.

A short routine

When the MacBook feels hot:

1. Move it to a hard surface with free vents.
2. Open Foreman and sort the Processes page by CPU, then by GPU.
3. Decide for the top app: wait, quit, or Efficiency Mode.
4. Watch the figures for a minute.

Foreman is $12 once, works on up to 3 Macs, and runs free for 24 hours so you can check it against your own hot Mac. The steps above need nothing else to start: moving the laptop off a soft surface and quitting an app you are not using often solve it.