Open Activity Monitor to see what's using your CPU

The fastest way to check processor usage on your Mac is to open Activity Monitor, which shows you every program running and how much CPU power each one is using. You can find it three ways: press Command + Space, type "Activity Monitor", and press Enter; or open Finder, click Applications, then Utilities, then double-click Activity Monitor; or click the Spotlight icon in the top-right corner of your screen and search for it.

When Activity Monitor opens, you are already on the CPU tab by default. The list shows every active process on your Mac. The %CPU column on the right tells you what percentage of your processor each program is using right now. If a program shows 0.0, it is running but barely using the processor. If it shows 50.0 or higher, that program is consuming a significant chunk of your CPU power.

The numbers change constantly because processor usage is live data. A program might show 2.0% one second and 15.0% the next, depending on what it is doing at that moment. This is normal. What matters is whether something stays high for minutes at a time, which suggests the program is working hard on a task or is stuck.

Key Takeaways

  • Activity Monitor shows CPU usage for every running program and opens in seconds from Spotlight or Applications > Utilities.
  • The %CPU column displays how much processor power each program is using right now, and the numbers update constantly as tasks change.
  • Programs using 80% or higher CPU for extended periods are usually the reason your Mac feels slow or your fan runs loud.
  • You can force-quit a frozen or stuck program by selecting it and clicking the stop button, which frees up processor power when ready.
  • The System Memory tab shows RAM usage instead of CPU, which is a separate measure of whether your Mac is running out of working memory.

Understand what the numbers mean

Your Mac's processor has a maximum capacity. On a single-core processor, 100% means the processor is completely full. On a multi-core processor (which most modern Macs are), 100% means all cores combined are at maximum. If you see one program at 80% and another at 30%, your processor is running at 110% total — which is impossible on a single core, so macOS is splitting the work across multiple cores.

A program using 5% to 15% is normal for background tasks like email checking, cloud syncing, or system processes. A program using 30% or higher is actively working on something — rendering video, compiling code, or processing a large file. A program using 80% or higher for more than a few seconds is either stuck, or it is genuinely doing heavy work and your Mac will feel slow until it finishes.

The Threads column shows how many parallel tasks a program is running. More threads usually means the program is designed to use multiple processor cores at once, which is efficient. Fewer threads means the program is older or simpler and uses only one core, which limits how fast it can work.

Sort by CPU usage to find the culprit

Click the %CPU column header once to sort all programs by processor usage, highest to lowest. The program using the most CPU appears at the top. This is the fastest way to spot what is slowing your Mac down. If the top program is something you recognize and you just started a heavy task (like exporting video or uploading files), that is expected and normal.

If the top program is something you did not start, or if it is using high CPU when you are not doing anything, that is a sign something is wrong. Look for programs with unfamiliar names. If you do not recognize a process, search for its name online — many system processes have technical names that sound suspicious but are harmless.

Some programs that legitimately use high CPU include Xcode (if you are coding), Final Cut Pro (if you are editing video), Chrome or Safari (if you have many tabs open), and Zoom (during a call). If you see one of these at the top and you are using that program, your Mac is working as designed.

Force-quit a frozen or stuck program

If a program is using 95% or higher CPU and is not responding to clicks, it is likely frozen. Select it in Activity Monitor and click the stop button (the circle with an X) in the top-left corner of the window. A dialog will appear asking whether you want to force-quit. Click Force Quit. The program will close when ready and free up that processor power.

Force-quitting is safe — it does not damage your Mac or other programs. You will lose any unsaved work in that program, but everything else stays intact. After force-quitting, you can reopen the program normally. If it freezes again when ready, the program may have a bug or may not be compatible with your version of macOS.

Check memory usage separately from CPU usage

CPU usage and memory usage are different things. A program can use a lot of CPU (processor power) without using much memory, or vice versa. If your Mac is slow but CPU usage is low, the problem is likely memory, not the processor. Click the Memory tab in Activity Monitor to see how much RAM each program is using.

The Memory tab shows the same list of programs but with different columns: Real Memory, Virtual Memory, and Memory Pressure. Real Memory is what matters most — it is the actual RAM your program is using. If one program shows 2000 MB or higher, it is using a significant amount of RAM. If Memory Pressure at the bottom is yellow or red, your Mac is running out of RAM and needs to use the hard drive as backup, which is much slower.

Monitor CPU usage over time with the Dock icon

Activity Monitor has a Dock icon option that shows CPU usage at a glance without opening the full window. Open Activity Monitor, click the Window menu, and select Dock Icon. Choose "Show CPU Usage" from the submenu. Now the Activity Monitor icon in your Dock will display a small graph showing your CPU usage in real time. Glance at it whenever your Mac feels slow to see if the processor is maxed out.

This is useful if you want to keep an eye on CPU usage while you work without keeping Activity Monitor open. The graph updates every second and shows the last 60 seconds of history, so you can see whether usage is climbing, staying steady, or dropping.

Restart your Mac if CPU usage stays high with nothing running

If Activity Monitor shows high CPU usage even when you are not running any programs, or if you see unfamiliar processes using CPU constantly, restart your Mac. Many temporary issues — stuck background processes, memory leaks, or system glitches — clear up after a restart. Click the Apple menu, select Restart, and let your Mac shut down and start fresh.

If CPU usage is still high after a restart, and you see the same unfamiliar process at the top of the list, that process may be malware or a problematic system extension. Search for the process name online to confirm what it is. If it is malware, you may need to use a dedicated removal tool or contact Apple Support.

Frequently Asked Questions

Why does my Mac fan run loud when CPU usage is high?

Your Mac's fan speeds up to cool the processor when it is working hard. High CPU usage generates heat, and the fan pulls cool air through the case to prevent overheating. This is normal and protective. If the fan is loud but CPU usage is low, the problem may be dust blocking airflow, and you should have your Mac cleaned by a technician.

Is 100% CPU usage bad for my Mac?

Short bursts of 100% CPU usage are fine — your Mac is designed to handle it. If a program uses 100% CPU for hours, it may be stuck or have a bug, and you should force-quit it. Sustained 100% usage also generates heat and drains battery faster on a laptop, so it is worth investigating if it happens often.

What is the difference between %CPU and %User?

Activity Monitor shows %CPU by default, which is the total processor usage. Some versions also show %User (time spent on user programs) and %System (time spent on system tasks). For most purposes, %CPU is all you need. If you see a program with high %System but low %User, it is doing system-level work that may be legitimate or may indicate a problem.

Can I see CPU usage without opening Activity Monitor?

Yes. You can add the CPU usage widget to your Mac's notification center by opening Notification Center (click the clock in the top-right corner), scrolling to the bottom, clicking Edit, and searching for Activity Monitor. You can also use the Dock icon option described above to see a live graph in your Dock.

Why does Safari use so much CPU?

Safari uses CPU when it is loading web pages, playing videos, or running JavaScript on websites. If Safari is using 50% or higher CPU when you are just reading a page, the website may have poorly optimized code or auto-playing video. Try closing unused tabs, disabling extensions, or switching to a different website to see if CPU usage drops.