How to Best Use Activity Monitor on Mac
Activity Monitor is the built-in macOS tool for checking what your Mac is doing in the background. It shows which apps and processes are using the processor, memory, energy, disk, and network. If a Mac feels slow, the fans are loud, the battery drains quickly, or an app stops responding, Activity Monitor is one of the first places to look.
The goal is not to close every process you do not recognize. macOS runs many background services that are normal. Activity Monitor is most useful when you use it to spot patterns: one app using unusually high CPU, memory pressure staying yellow or red, a browser using a large amount of energy, or a process that is marked as not responding.
How to open Activity Monitor
The quickest way to open Activity Monitor is with Spotlight. Press Cmd+Space, type Activity Monitor, then press Return. You can also find it in Applications, Utilities, Activity Monitor.
Once it is open, the main tabs across the top are CPU, Memory, Energy, Disk, and Network. Each tab shows a different view of system activity. You can click column headings to sort by the highest usage. This is usually the easiest way to find the app or process using the most resources.
Activity Monitor tabs at a glance
| Tab | What it shows | Best use |
|---|---|---|
| CPU | Processor use by apps and background processes. | Checking slow performance, loud fans, and heavy apps. |
| Memory | RAM use, memory pressure, cached files, and swap use. | Checking whether the Mac is short on memory. |
| Energy | Energy use by apps and recent battery impact. | Checking battery drain on MacBooks. |
| Disk | Data read from and written to storage. | Checking heavy file activity, syncing, exports, and backups. |
| Network | Data sent and received by processes. | Checking uploads, downloads, cloud sync, and background traffic. |
Use the CPU tab for slow performance
The CPU tab shows how much processor capacity each app or process is using. Click the % CPU column to sort the list. If one app is using a high amount of CPU for a long time, it may explain why the Mac feels slow or why the fans are running.
High CPU is not always a problem. Video exports, software updates, photo indexing, game updates, browser tabs, code builds, and large spreadsheet calculations can all use more CPU temporarily. The question is whether the high usage matches what you are doing.
Real-world example: if Safari or Chrome is using a large amount of CPU and the Mac feels warm, the cause may be one website, video, extension, or web app. Quit unused tabs, restart the browser, or test the same task in another browser. If a video editor is exporting a file, high CPU is expected until the export finishes.
Understand System, User, and Idle
At the bottom of the CPU tab, Activity Monitor shows System, User, and Idle. System is CPU used by macOS processes. User is CPU used by apps you opened and processes started by those apps. Idle is the unused processor capacity.
If Idle is high, the processor is not the reason the Mac feels slow. If Idle is very low for a long time, look at the top of the CPU list and check which apps or processes are using the most CPU.
Use the Memory tab for RAM pressure
The Memory tab is often more useful than simply looking at how much RAM is used. macOS is designed to use available memory for active apps, cache, and system tasks. A high memory-used number is not automatically bad.
The main item to watch is Memory Pressure. Apple describes green memory pressure as efficient RAM use, yellow as a sign the Mac might eventually need more RAM, and red as a sign the Mac needs more RAM for the current workload.
Real-world example: if Memory Pressure is green while you have a browser, email, Messages, and a few documents open, the Mac is handling the workload. If Memory Pressure turns yellow or red while you have many browser tabs, a large spreadsheet, photo editing software, and video calls open, the Mac may be short on memory for that task.
Watch swap and compressed memory
Swap Used shows how much data macOS has moved between memory and storage. Some swap is normal. Heavy swap combined with yellow or red memory pressure can make a Mac feel slower because storage is being used to help manage memory.
Compressed Memory shows memory that macOS has compressed to make better use of available RAM. Compression is normal. If the Mac often feels slow and Memory Pressure is frequently yellow or red, the workload may be too heavy for the installed RAM.
Use the Energy tab for battery drain
The Energy tab is useful on MacBooks. It shows which apps are using more energy now and which have used more energy recently. If battery life drops faster than expected, sort by Energy Impact or 12 hr Power to see which apps are contributing.
Real-world example: if a video meeting app, browser, or cloud-sync app has a high energy impact, that may explain short battery life. Closing unused apps, reducing browser tabs, lowering screen brightness, pausing large uploads, or restarting a problem app can help.
Energy use changes constantly. A short spike does not always mean anything is wrong. Look for apps that stay high over time or appear high when you are not actively using them.
Use the Disk tab for file activity
The Disk tab shows how much data apps and processes are reading from and writing to storage. This can help when the Mac feels busy even though you are not doing much on screen.
Real-world example: Time Machine backups, iCloud Drive sync, photo libraries, software updates, video exports, and large downloads can all create disk activity. If storage activity is high, let the current task finish if it is expected. If it is unexpected, sort the Disk tab and check which process is reading or writing the most data.
Use the Network tab for internet activity
The Network tab shows data sent and received by apps and processes. It can help when your internet connection feels slow, cloud files are syncing, or an app seems to be uploading or downloading in the background.
Real-world example: if iCloud Drive, Photos, Dropbox, OneDrive, a browser, or a game launcher is sending or receiving a lot of data, other internet tasks may feel slower. Pause syncing, close unused apps, or wait for the transfer to finish.
How to quit an app or process
If an app is not responding, Activity Monitor can quit it. Select the app or process, then click the stop button in the upper-left corner of the Activity Monitor window. Choose Quit first when possible. Use Force Quit only when the app will not close normally.
Be careful with processes you do not recognize. Some are system services, drivers, helpers, or background tasks that macOS or installed apps need. Quitting the wrong process may cause an app to close, a service to restart, or a feature to stop until the Mac is restarted.
When not to quit a process
Do not quit processes just because they have unfamiliar names. Activity Monitor shows many items that are not regular apps. Some are part of Spotlight indexing, iCloud, printer tools, security services, audio, graphics, Bluetooth, networking, or macOS itself.
A better approach is to identify the pattern first. If a process is high for a few seconds, wait. If it stays high for several minutes and the Mac is slow, search the process name, check which app it belongs to, and quit the related app before forcing the process to stop.
Practical checks for common Mac problems
| Problem | Where to look | What to check |
|---|---|---|
| Mac feels slow | CPU and Memory | High % CPU, low Idle, yellow or red Memory Pressure. |
| Battery drains quickly | Energy | Apps with high Energy Impact or high 12 hr Power. |
| Fans are loud | CPU | Apps using high CPU for a long period. |
| Internet feels slow | Network | Apps sending or receiving large amounts of data. |
| Storage seems busy | Disk | Backups, cloud sync, downloads, or large file exports. |
| App is frozen | CPU or search bar | Process marked Not Responding, then use Quit or Force Quit. |
Use the search field
Activity Monitor can show hundreds of processes. The search field is useful when you know the app or process name. For example, search Safari, Chrome, Dropbox, OneDrive, Photos, Excel, or Mail to see related processes. This is cleaner than scrolling through the full list.
If you are checking a browser, remember that one browser can run many helper processes. A high browser process may come from one tab, extension, web app, or video. Close tabs one at a time if you want to isolate the cause.
Change the Dock icon view
Activity Monitor can show live activity in the Dock. With Activity Monitor open, choose View, Dock Icon, then select an option such as CPU Usage, CPU History, Network Usage, or Disk Activity. This can be useful while testing a problem because you can watch activity without keeping the full window open.
Activity Monitor for used Mac buyers
Activity Monitor can help when checking a used Mac, but it should not be the only test. Open the CPU and Memory tabs while using the Mac normally. Check whether the machine stays responsive, if Memory Pressure is green during light use, and whether any app or process is constantly using a high amount of CPU.
Also check battery condition, storage health, display condition, keyboard, trackpad, speakers, camera, ports, Wi-Fi, Bluetooth, and whether the Mac supports the macOS version you need. If you are comparing replacement options, browse our used computers collection and check each listing for model year, chip, memory, storage, condition, and included accessories.
Activity Monitor habits that help
Use Activity Monitor when you are diagnosing a specific issue. Check the right tab for the symptom, sort by the most relevant column, and compare what you see with what the Mac is doing. If the numbers match the task, there may be no problem. If they do not match the task, look more closely.
Restart the Mac if several apps are behaving strangely. Quit unused apps if memory pressure is high. Reduce browser tabs if a browser is using heavy CPU or memory. Pause cloud syncing if the network or disk is busy. Update apps if the same process repeatedly causes issues.
Final thoughts
Activity Monitor is most useful as a troubleshooting tool. The CPU tab helps identify processor load, Memory shows whether RAM is under pressure, Energy helps explain battery drain, Disk shows storage activity, and Network shows internet activity. Used together, these tabs can explain many common Mac slowdowns.
The best approach is to avoid guessing. Open Activity Monitor, sort the relevant tab, look for sustained high usage, and connect the result to what you are doing on the Mac. That gives you a clearer way to decide whether to quit an app, wait for a task to finish, restart the Mac, reduce your workload, or consider a Mac with more memory or stronger performance.