The fastest way to see what's using your processor

Open Activity Monitor — the built-in tool that shows you exactly what's running on your Mac and how much processor power each program is using. Press Command+Space to open Spotlight search, type "Activity Monitor", and press Enter. The CPU tab opens by default and shows you every running process, ranked by how much processor it's using right now.

The top of the window displays your overall CPU usage as a percentage. If you see a number close to 100%, your Mac is working hard and may feel slow. The list below shows individual programs and background processes, with the heaviest users at the top. One program using 80% or more usually means that's what's slowing things down.

Activity Monitor stays open while you work, so you can watch usage change as you open and close programs. Close it by pressing Command+W or clicking the red button in the top-left corner.

Key Takeaways

  • Activity Monitor is built into every Mac and shows CPU usage instantly without installing anything.
  • The CPU tab displays overall processor usage at the top and lists every running program ranked by how much it's using.
  • A single program using 80% or more CPU usually means that program is the reason your Mac feels slow.
  • You can force-quit programs that are stuck or using too much power by selecting them and clicking the stop button.
  • The %CPU column shows current usage; the Time column shows total processor time since the program started.

Understanding the columns in Activity Monitor

The CPU tab displays several columns of information. The %CPU column shows what percentage of your processor each program is using right now — this number changes constantly as programs do different tasks. The Time column shows the total amount of processor time that program has used since it started, which helps you spot programs that have been running inefficiently for a long time.

#Threads shows how many separate tasks that program is running at once. Most programs use between one and ten threads; a program with hundreds of threads may be stuck or malfunctioning. The User column shows who started the program — your username for programs you opened, "root" for system processes, or other usernames for background services.

You do not need to understand every column. Focus on the %CPU number and the program name. If one program shows 50% or higher and your Mac feels slow, that program is the problem.

When one program is using too much CPU

If a single program is using 80% or more of your CPU and your Mac is sluggish, try closing that program normally first — click the program name in the menu bar and select Quit. Wait a few seconds and check Activity Monitor again to confirm it closed.

If the program does not close or keeps reappearing in the list, select it in Activity Monitor and click the stop button (the circle with an X) in the toolbar at the top. A dialog box will ask whether you want to force quit. Click Force Quit to shut it down immediately. This can cause you to lose unsaved work in that program, but it stops the runaway process.

After force-quitting, restart your Mac if the same program keeps using high CPU when you reopen it. If the problem continues, the program may have a bug or compatibility issue with your version of macOS, and you may need to update it or contact the developer.

Checking CPU usage over time

Activity Monitor shows you what is happening right now, but sometimes you need to see patterns over hours or days. The Window menu in Activity Monitor includes an option called CPU History — click it to open a graph that shows your overall CPU usage over the last hour. The graph updates in real time as your Mac works.

This graph is useful for spotting programs that spike at certain times. For example, if you see a spike every morning at 9 a.m., a scheduled backup or update may be running. If the graph shows constant high usage, a background process is probably always active.

You can also open the Memory tab in Activity Monitor to check whether programs are using too much RAM instead of CPU. Some programs use a lot of memory, which can slow your Mac even if CPU usage looks normal. The same force-quit method works for memory hogs.

System processes and what they do

Activity Monitor shows many processes with names like "kernel_task", "WindowServer", and "Finder". These are part of macOS itself, not programs you installed. Kernel_task often shows high CPU usage, but this is normal — it is how macOS manages the processor and does not mean something is wrong.

WindowServer handles your display and graphics, so it uses more CPU when you have many windows open or are watching video. Finder is the file browser, and it uses CPU when you are browsing folders or searching for files. These processes should drop back to low usage when you are not actively using them.

Do not force-quit system processes. If a system process is stuck at high CPU usage and your Mac feels frozen, restart your Mac instead. Hold the power button for ten seconds until your Mac shuts down, then press it again to turn it back on.

Why your Mac feels slow even with low CPU usage

Sometimes Activity Monitor shows low CPU usage but your Mac still feels sluggish. This usually means the problem is not the processor — it is either the hard drive or SSD working hard, or your Mac running out of memory. Check the Memory tab in Activity Monitor to see how much RAM you are using. If the number is close to your Mac's total memory (shown at the bottom), your Mac is out of space and will slow down.

To check disk activity, click the Disk tab. If you see high numbers in the Read/Write columns, your hard drive or SSD is working hard. This is common when you first start your Mac or after an update, but it should drop to near zero after a few minutes. If disk activity stays high for hours, a background process may be indexing files or backing up data.

Restarting your Mac clears memory and stops most background tasks, which often fixes slowness that is not caused by CPU usage. If slowness returns immediately after restart, Activity Monitor will help you identify what is running.

Frequently Asked Questions

Is it normal for CPU usage to jump around?

Yes. CPU usage changes constantly as programs do different tasks. A program might use 5% one second and 50% the next. What matters is whether it stays high — if a program is consistently above 50% when you are not actively using it, that is a problem.

Can I close Activity Monitor without affecting my Mac?

Yes. Activity Monitor is just a tool for watching what your Mac is doing. Closing it does not stop any programs or change anything on your Mac. You can open and close it as many times as you want.

What does "Not Responding" mean in Activity Monitor?

It means the program is frozen and not responding to clicks or keyboard input. Force-quit it by selecting it and clicking the stop button. The program will close immediately, and you can reopen it.

Why does my Mac use CPU even when I am not doing anything?

Background processes are always running — Spotlight indexing files, Time Machine backing up, system updates checking, and cloud services syncing. This is normal. If CPU usage stays above 20% when you are not using your Mac, check Activity Monitor to see which process is active.

Should I worry about high CPU usage for a few seconds?

No. Brief spikes are normal when you open programs, save files, or watch video. Only worry if a program stays above 50% for several minutes while you are not actively using it.