How to check memory usage on a Mac
Updated 13 October 2026
To see what is using memory on a Mac, open Activity Monitor, choose the Memory tab and sort by the Memory column; the Memory Pressure graph at the bottom tells you whether that usage is actually a problem. In Terminal, top -l 1 -o mem -n 10 lists the biggest processes and memory_pressure prints the system-wide free memory percentage.
The rest of this guide explains how to read those numbers, because "used memory" on a Mac is often high for good reasons. If you prefer a menu-bar view, WTMemory shows memory usage, macOS pressure events and the apps behind them, but every step below works with built-in tools.
How do I check RAM usage in Activity Monitor?
- Open Activity Monitor from Applications > Utilities, or press Command-Space and type its name.
- Select the Memory tab.
- Click the Memory column header so the largest processes are at the top.
- Read the panel at the bottom of the window.
The bottom panel shows these figures:
| Figure | What it means |
|---|---|
| Physical Memory | The RAM installed in your Mac. |
| Memory Used | App Memory plus Wired Memory plus Compressed. |
| App Memory | Memory allocated by apps and their processes. |
| Wired Memory | Memory the system must keep in RAM and cannot compress or swap. |
| Compressed | Inactive memory macOS has compressed to make room, instead of writing it to disk. |
| Cached Files | Recently used file data kept in RAM. macOS gives it back to apps when they need it. |
| Swap Used | Memory written out to the startup disk because RAM ran short. |
One process row is not always the whole app. Browsers and Electron apps split work into many helper processes, so a browser with 40 tabs can appear as dozens of rows. Add them up, or use View > All Processes, Hierarchically to group them.
What is the difference between memory used and memory pressure?
Memory used is how much RAM is allocated right now. Memory pressure describes how hard macOS has to work to keep handing out memory. The graph is colour coded: green means memory is being used efficiently, yellow means macOS is relying on compression, and red means it is short of memory and leaning on swap.
A Mac with 8 GB of RAM can show 7.5 GB used and green pressure all day. That is normal. macOS treats unused RAM as wasted RAM and fills it with cached files, which it drops instantly when an app needs the space. Pressure, not the used figure, is the number to watch.
What do swap and compressed memory tell me?
When RAM fills up, macOS first compresses inactive pages, which is fast. If that is not enough, it writes pages to a swap file on the startup disk, which is much slower than RAM. Some swap is normal, especially after a long session. The warning signs are:
- Swap Used growing steadily while you work, not just sitting at a fixed figure.
- The pressure graph spending long periods in yellow or red.
- Apps hesitating when you switch between them.
Check swap from Terminal with:
sysctl vm.swapusageHow do I check memory usage from Terminal?
These commands only read information. None of them closes apps or changes settings.
Top memory users. Take one snapshot sorted by memory and show the top 10 processes:
top -l 1 -o mem -n 10 -stats pid,command,memSystem pressure. Run memory_pressure with no arguments. It prints page statistics and ends with a line such as "System-wide memory free percentage: 37%". Do not add -l, -p or -S: those options deliberately apply or simulate memory pressure, according to man memory_pressure.
memory_pressureRaw page counts. vm_stat prints page counts. Multiply by the page size shown in the first line (16384 bytes on Apple Silicon, 4096 on Intel) to get bytes. Watch "Pages stored in compressor", "Swapins" and "Swapouts"; run vm_stat 5 to print a new line every 5 seconds and see whether swapping is happening now.
vm_statInstalled RAM. sysctl hw.memsize prints total RAM in bytes, for example 8589934592 for 8 GB.
What is usually using all my memory?
On developer and AI-heavy Macs, the same few things come up again and again:
- Browsers. Every tab, extension and service worker can be its own process. Close tabs you are not using, or check the browser's own task manager.
- Electron apps. Slack, Discord, VS Code, Cursor and similar apps each run their own copy of a browser engine with several helper processes.
- Docker Desktop. Containers run inside a Linux virtual machine, and that VM reserves memory up to the limit set in Docker Desktop settings, under Resources. Lower the limit if you rarely need it, or quit Docker when you are not using containers. See the Docker disk space guide for the storage side.
- Local LLMs. A loaded model sits in memory roughly the size of its weights. With Ollama,
ollama psshows which models are loaded andollama stop <model>unloads one. LM Studio has an eject control for loaded models. - Dev servers and watchers. Forgotten
npm run dev, Vite, Next.js, webpack or Python servers keep running in old terminal tabs. List what is listening withlsof -iTCP -sTCP:LISTEN -n -P, then see the port 3000 guide before stopping anything. - Virtual machines and simulators. Parallels, UTM and iOS Simulator reserve memory while they run.
Does "freeing RAM" actually help?
Usually not, and it is worth being honest about why. A lot of "used" memory is cached data that macOS will give back the moment an app asks for it. Forcing that cache out means macOS has to read the same data from disk again later. "Memory cleaner" apps that show a big drop in used memory are often showing exactly this: a number going down, not a faster Mac.
What does help when pressure is yellow or red:
- Quit the app or process at the top of the Memory column, if you do not need it.
- Unload local models and stop containers you are not using.
- Close idle browser tabs and windows.
- Restart a single app that has grown far beyond its normal size, which can happen with long-running processes.
- If pressure is red during your normal daily work, your workload needs more RAM than the Mac has.
Is there a quicker way to watch memory on a Mac?
WTMemory is a small native menu-bar app that shows memory usage, macOS memory pressure events, CPU, disk, battery and network readings, plus a Running Apps list with each app's memory, CPU, PID and ports. Inspection is free. With Pro ($9 USD once, up to 3 Macs, 7-day trial) you can quit apps after confirmation, protect apps you want to keep, and use "Keep Current App, Close the Rest" to ask other apps to close normally after you review the list.
It also has a "Clear Inactive Memory" menu action, an optional manual macOS memory reset that may ask for administrator approval. Apps may reload cached data afterward, and we do not promise it makes anything faster, for the reasons above. WTMemory needs macOS 12 or later and runs natively on Apple Silicon and Intel; the download is about 4.2 MB.
FAQ
Is high memory usage bad on a Mac?
Not by itself. macOS deliberately fills spare RAM with cached files and compressed data. Memory pressure is the better signal: green is fine, yellow means macOS is working harder, red means it is short of memory.
What is the difference between memory used and memory pressure?
Memory used is how much RAM is currently allocated. Memory pressure describes how hard macOS has to work to keep giving apps memory, using compression and swap. A Mac can show high usage with low pressure.
Why is swap used when I still have free memory?
macOS can move rarely used pages to swap earlier in a session and leave them there. A small, stable swap figure is normal. Swap that keeps growing while you work means your workload is larger than your RAM.
Does freeing RAM speed up a Mac?
Usually not. Clearing cached memory just makes macOS read that data from disk again later. Closing the app that is causing high memory pressure is what helps.
Is the memory_pressure command safe to run?
Run without arguments, memory_pressure prints statistics and the system-wide free memory percentage. The -l, -p and -S options deliberately apply or simulate pressure, so avoid them unless you are testing.