Activity Monitor on Mac: How to Check CPU Usage and Find What's Slowing You Down
Activity Monitor is the Mac's answer to Windows Task Manager. It shows every app and background process, how much CPU, memory, energy, disk and network each is using, and lets you stop the ones misbehaving. It's also full of cryptic process names, which is why most people open it, see WindowServer at 40% and kernel_task at 300%, and close it again in alarm. Here's how to read it.
Quick answer: Open Activity Monitor from Applications → Utilities (or press ⌘Space and type "Activity Monitor"). Click the CPU tab and sort by % CPU to see what's using the processor. % CPU is per core, so 200% means two full cores. To stop something, select it, click the ✕ button and choose Quit (or Force Quit if it's frozen). Don't quit kernel_task or WindowServer: kernel_task is macOS cooling the chip, and WindowServer draws everything on your screen. For a history of what's been using your CPU rather than a snapshot, MacCove Space keeps CPU, memory and battery trends by app.
The five tabs
| Tab | What it shows | Use it when |
|---|---|---|
| CPU | Processor use by each process, plus System, User and Idle totals | Fans are loud, the Mac is sluggish or hot |
| Memory | Memory used by each process, plus memory pressure and swap | Apps are slow to switch, you see "out of application memory" |
| Energy | Each app's energy impact and whether it's preventing sleep | Battery drains fast, Mac won't sleep |
| Disk | Data read and written by each process | Disk is constantly busy, Mac stalls |
| Network | Data sent and received by each process | Network is slow, or you're curious what's talking to the internet |
The memory side has its own guide: how to check memory usage on a Mac.
How to read the CPU tab
Click the % CPU column header so the busiest processes are at the top. Then check:
% CPU is relative to a single core. An M-series Mac has many cores, so a process can legitimately show 300% or more. What matters is whether it stays high while you're not using it.
CPU Time is how much processor time a process has used since it started. A huge number on something you never use is a clue.
Kind shows Apple or Intel. Intel apps run through Rosetta on Apple silicon Macs, which costs extra CPU.
At the bottom, System is macOS, User is your apps, and Idle is unused capacity. A healthy Mac at rest is mostly Idle.
For a longer view, choose Window → CPU History, or View → Dock Icon → Show CPU Usage to keep a live graph in the Dock.
Common processes and what they mean
| Process | What it is | When it's busy | Should you quit it? |
|---|---|---|---|
| kernel_task | The core of macOS | High CPU when the Mac is hot; it limits other processes to cool the chip | No. Fix the heat instead |
| WindowServer | Draws every window on every display | Many windows, tabs, Spaces or displays; screen recording | No. Close windows instead |
| mds, mds_stores, mdworker | Spotlight indexing | After updates, migrations or connecting big drives | No. Let it finish |
| photoanalysisd, mediaanalysisd | Photos analysing faces, objects and duplicates | After importing lots of photos | Better to let it finish, ideally on power |
| cloudd, bird | iCloud sync | Uploading or downloading lots of files | No. Let it finish or pause the sync |
| backupd | Time Machine | During a backup | No |
| softwareupdated | Software updates | Downloading or preparing an update | No |
| Google Chrome Helper (Renderer) | One browser tab or extension | A heavy web page | Close the tab instead |
A rule of thumb: if a system process is busy right after an update, an import or a migration, it's usually doing a one-off job and will calm down. If it's busy all the time for days, something is wrong. Restart, update, and search the process name.
Why WindowServer uses so much CPU
WindowServer composes everything you see: every window, shadow, animation and external display. Its load goes up with the number of open windows and browser tabs, Spaces, Stage Manager, multiple or high-resolution displays, and screen recording or sharing. Closing windows you aren't using, quitting apps rather than just closing their windows, and using fewer displays all help. Some people also find Reduce transparency and Reduce motion (System Settings → Accessibility → Display) make a difference on older Macs.
Why kernel_task uses so much CPU
Apple explains that one of kernel_task's jobs is to manage CPU temperature. When the chip gets too hot, kernel_task makes the CPU less available to the processes driving the heat, so it appears to use lots of CPU itself. It doesn't cause the heat and backs off once things cool down. The fix is to deal with the heat: give the Mac airflow, quit the heavy app, and check the room isn't too warm. More in MacBook overheating and battery drain.
How to quit a process safely
Select the process in Activity Monitor.
Click the ✕ (Stop) button at the top left.
Choose Quit first. The process quits when it's safe to, saving its work.
If it doesn't respond, choose Force Quit. It stops immediately and you may lose unsaved changes.
Don't force quit system processes you don't recognise. macOS will usually restart them anyway, and some will log you out or restart your Mac.
Useful features most people miss
| Feature | Where | What it's for |
|---|---|---|
| Show all processes, hierarchically | View → All Processes, Hierarchically | See which helper belongs to which app |
| Search | Search field, top right | Find a process by name |
| Inspect | ⓘ button | Open files, ports and memory of one process |
| Sample Process | ⋯ button → Sample Process | A 3-second report useful to developers or support |
| Update frequency | View → Update Frequency | Refresh more often while diagnosing |
| GPU History | Window → GPU History | Check graphics load during games or video work |
In Terminal, top -o cpu gives a similar live list sorted by CPU.
When Activity Monitor isn't enough
Activity Monitor tells you what is busy right now. It doesn't tell you which background helper belongs to which app you installed two years ago, or keep a history of what was eating your CPU this morning. MacCove Space shows CPU, GPU, memory, network, disk and battery trends over time, groups processes by the app they belong to, and lets you quit runaway processes or switch off the login items that start them. For a broader checklist, see why your Mac is running slow.
FAQs
What is the Task Manager on a Mac?
Activity Monitor. To force quit an app quickly without opening it, press ⌥⌘Esc.
Why is my Mac's CPU at 100% when nothing is open?
Usually a background job: Spotlight indexing, Photos analysis, iCloud sync or a backup, especially after an update. Check the top process in the CPU tab. If it's an app's helper, quit the app or remove its login item.
Is high CPU usage bad for my Mac?
Short bursts are normal. Sustained high CPU makes the Mac hotter and drains the battery faster, and macOS will throttle performance to keep temperatures safe.
How do I see CPU usage in the menu bar?
Activity Monitor can show CPU use in the Dock icon (View → Dock Icon). For a menu bar display, you need a third-party app.
Related guides
Why Is My Mac Running Slow?
How to Check Memory Usage on a Mac
MacBook Overheating and Battery Draining Fast