How to open Activity Monitor
- Spotlight: press Command-Space, type "Activity Monitor" and press Return.
- Finder: open Applications › Utilities › Activity Monitor.
- The Dock: while it's open, Control-click its Dock icon and choose Options › Keep in Dock, so it's one click away next time.
Activity Monitor refreshes every 5 seconds by default; View › Update Frequency changes that (Apple). The View menu also filters the list: All Processes, My Processes, System Processes, Windowed Processes (usually apps) and a few more (Apple). When you're hunting for a problem, use All Processes, so nothing is hidden. Click any column heading to sort by it, and double-click a process for details.
CPU: who is using the processor
Sort by % CPU. The figure is per core, so one fully busy thread reads about 100%, and a busy app on a Mac with several cores can show well over 100%. We checked this on macOS 27.0.1: a single-threaded test loop settled at 99.5%. It also means the total of the column can be far more than 100%.
At the bottom, Apple defines three figures (Apple, View CPU activity):
- System: the share used by processes that belong to macOS.
- User: the share used by apps you opened and the processes they started.
- Idle: the share nothing is using.
What's normal: short spikes when you open an app, load a web page or export something are expected; they come and go within seconds. Worth acting on: one app staying high while you're not using it, or Idle staying low for minutes with nothing running. Window › CPU History shows a graph per core, which makes a stuck app easy to spot.
Memory: read the pressure graph, not "Memory Used"
The Memory tab shows how much memory each process uses, and a summary at the bottom. The one thing to read there is Memory Pressure. Apple says it's determined by free memory, swap rate, wired memory and file cached memory, and it explains the colors like this (Apple, Check if your Mac needs more RAM):
| Color | What Apple says | What to do |
|---|---|---|
| Green | Your Mac is using its RAM efficiently | Nothing |
| Yellow | Your Mac might eventually need more RAM | Quit apps you aren't using; watch it |
| Red | Your Mac needs more RAM | Quit the biggest app you can spare now |
The figures beside the graph, as Apple defines them (Apple, View memory usage):
- App Memory: memory used by apps.
- Wired Memory: memory the system needs, which must stay in RAM.
- Compressed: memory that has been compressed to make more RAM available.
- Cached Files: files the system keeps in unused memory to improve performance.
- Swap Used: space on your startup disk used to swap unused data to and from RAM.
That's why Memory Used near the total isn't a problem: a lot of it is cached files, which macOS gives back the moment an app needs the room. Some swap is normal too. Swap that keeps growing while the graph is yellow or red is the sign your Mac is short of memory for what you're running.
Energy: Energy Impact, 12 hr Power and Preventing Sleep
The Energy tab answers "what's using my battery?". Apple's definitions (Apple, View energy consumption):
- Energy Impact: a relative measure of the app's current energy use; lower is better.
- 12 hr Power: the app's average energy impact over the last 12 hours, or since the Mac started. Only on Mac laptops.
- App Nap: whether App Nap is active for the app.
- Preventing Sleep: whether the app is stopping your Mac from sleeping.
Energy Impact is useful for ranking apps on one Mac at one moment. Apple gives it no units, though, so you can't turn it into watts or hours of battery, and it's best treated as a ranking on one Mac rather than a score to compare between Macs. Sort by 12 hr Power to catch an app that drained the battery in bursts while you weren't looking. A "Yes" under Preventing Sleep is the first thing to check when a MacBook won't sleep or loses charge with the lid closed; why your MacBook loses charge while asleep covers that case.
Disk and Network: when they matter
Most days you can skip these two tabs. The Disk tab counts how often each process reads from and writes to the disk, and how much data it moves (Apple). It's worth a look when the Mac feels sluggish but the CPU is idle: sync clients, backups and indexing show up here first.
The Network tab shows packets and data sent and received, in total and per second (Apple). Use it when your connection feels slow and you suspect something on the Mac is uploading or downloading in the background, such as a cloud backup or a large update.
Quit, Force Quit and Sample Process
Select a process, click the Stop button in the top-left corner of the window, then choose (Apple, Quit an app or process):
- Quit works like File › Quit: the process quits when it's safe to, and doesn't quit if that could lose data or disturb another app.
- Force Quit ends it immediately. If it has files open, you may lose data, and apps or processes that depend on it can have problems.
A process shown in red with "(Not Responding)" has stopped answering. Before you force quit something you'd like fixed, click the More button and choose Sample Process: it records what the process is doing over 3 seconds, the kind of report developers ask for when you file a bug (Apple, Run system diagnostics).
What's safe to quit? Your own apps, always, as long as you've saved your work. Be wary of system processes: they belong to macOS, most of them are doing a job you can't see, and quitting them rarely fixes anything. If Activity Monitor asks for an administrator password, that's because you're trying to quit a process you don't own. Treat that as a reason to stop and look the name up first.
Processes you'll see, and what they mean
| Process | What it does | More |
|---|---|---|
| kernel_task | The core of macOS. High CPU on a warm Mac means it's holding back other work to manage heat | kernel_task |
| WindowServer | Draws and combines every window on every display | WindowServer |
| mds_stores, mdworker_shared | Spotlight indexing | mds_stores |
| photoanalysisd, mediaanalysisd | On-device analysis of your photos and videos | mediaanalysisd |
If the Mac is slow and you're not sure which tab to start with, Why is my Mac so slow? gives an order to check them in.
How Tend helps
Energy Impact ranks apps but can't tell you how much power they use. Tend measures your Mac's total power draw and estimates each app's share in watts, so the list reads "Browser 3.6 W" rather than a unitless score. The per-app figures are estimates, and Tend says so. It keeps 24 hours of that history free (30 days with Pro), has Quit and Force Quit on every app, and with Pro can alert you when an app stays above 80% CPU for 5 minutes. Activity Monitor is still the better tool for Disk, Network and process sampling.
Questions
Where is Activity Monitor on my Mac?
It's in Applications › Utilities. The quickest way to open it is Spotlight: press Command-Space, type Activity Monitor and press Return.
What is memory pressure on a Mac?
Memory pressure is Activity Monitor's measure of how well your Mac's memory is keeping up, based on free memory, swap rate, wired memory and cached files. Green means memory is used efficiently, yellow means your Mac might eventually need more RAM, and red means it needs more than it has for what you're running.
What does Energy Impact mean?
Apple describes Energy Impact as a relative measure of an app's current energy use, where lower is better. It has no units, so it's good for ranking apps on one Mac but can't be converted to watts or compared between Macs.
Is it safe to quit processes in Activity Monitor?
Quitting your own apps is safe once your work is saved. Force Quit can lose unsaved data. Quitting macOS's own processes rarely fixes anything, and if Activity Monitor asks for an administrator password, the process isn't yours, so look it up before going ahead.
Why is my Mac using so much memory?
Because macOS keeps recently used files in spare memory to make things faster, so Memory Used is often close to the total. That's normal. Only worry if the Memory Pressure graph turns yellow or red.
Related guides
Why is my Mac so slow? How to find the cause
A five-minute diagnosis using these tabs
What is kernel_task, and why is it using so much CPU?
Usually heat management, not a fault
Why is my MacBook battery draining so fast?
The two-minute Energy tab check
Stats vs iStat Menus: which Mac system monitor?
If you'd like these numbers in the menu bar
Sources
- Apple, View information about Mac processes in Activity Monitor
- Apple, View CPU activity in Activity Monitor on Mac
- Apple, View memory usage in Activity Monitor on Mac
- Apple, Check if your Mac needs more RAM in Activity Monitor
- Apple, View energy consumption in Activity Monitor on Mac
- Apple, View disk activity and View network activity in Activity Monitor
- Apple, Quit an app or process in Activity Monitor on Mac
- Apple, Run system diagnostics in Activity Monitor on Mac
- Apple, Change how often information is updated in Activity Monitor
See your apps' energy use in watts
Tend is free to download. Pro is $1.99 a month, $12.99 a year with a 7-day free trial, or $29.99 once.