“Your system has run out of application memory” on Mac

What the message means

The warning appears in a window titled Force Quit Applications, with this text (as it reads on macOS 27.0.1):

• "Your system has run out of application memory."
• "To avoid problems with your computer, quit any applications you are not using."

Below it is a list of your open apps. Apps that macOS has paused to save memory are marked "(paused)", and the window has two buttons: Force Quit and Resume. Apple doesn't document this window in its support articles, so the description here comes from the window's own text in macOS.

It's a step beyond the yellow and red Memory Pressure that Activity Monitor shows. Before it gets here, macOS has already compressed memory and moved it out to swap files on the startup disk (Apple, View memory usage). The warning means that hasn't been enough.

What to do right now

1. Save your work in any app that still responds. Switch to it and press Command-S.
2. Choose an app to close. Pick the one you can lose most easily, ideally the heaviest: a browser with many tabs, a virtual machine, a video or photo editor, or a game. Select it in the list and click Force Quit. Unsaved changes in that app are lost.
3. Resume what you need. If an app you're working in shows "(paused)", select it and click Resume once you've made room, then save and quit anything else you don't need.
4. Check Activity Monitor. The warning only lists apps. The real culprit can be a background process or a browser's tab process. Open Activity Monitor, click Memory, sort by the Memory column and quit anything large you don't need, with the Stop button at the top left.
5. Check free disk space. Open System Settings › General › Storage. If it's nearly full, free some space now (see below).
6. Restart when you can. It empties memory and swap. If the Mac stops responding entirely, what to do when your Mac is frozen covers the recovery.

For quitting apps when the window itself doesn't respond, see every way to force quit on a Mac.

Why it happens

A Mac doesn't usually run out of memory just from normal use, because swap gives it room to spare. When it does, it's nearly always one of three things.

One app's memory kept growing

A bug in an app, a web page or an extension can make its memory use climb for as long as it runs. The sign is a single process in Activity Monitor using far more than everything else, and growing each time you look. Browsers are common cases, because every tab is its own process: in Activity Monitor, Chrome's tabs show as Google Chrome Helper (Renderer), and Safari's pages run in WebKit processes, not under the browser's own name.

The startup disk is nearly full

Swap lives on the startup disk. Apple's developer documentation says macOS uses no fixed partition for it and instead "uses all of the available space on the machine's boot partition" (Apple Developer, About the Virtual Memory System). On our MacBook Pro with macOS 27.0.1, swap was kept in 1 GB files in /System/Volumes/VM, and macOS added new ones as it needed them. When the disk has no room for another file, swap can't grow, and the warning comes much sooner than it would on a disk with space to spare.

More running than the Mac's memory can hold

Virtual machines, large photo or video projects, big code builds and dozens of tabs all at once can need more than RAM and swap together can supply. Apple's list of reasons a Mac runs slowly includes "an app you're using may require more memory than your Mac has easily available" (Apple, If your Mac runs slowly).

How to find the app that grew

In Activity Monitor's Memory tab, sort by Memory and watch the top of the list for a few minutes. A process whose number keeps rising while you aren't doing more with it is the one. Double-click it for details: the Memory tab of that window shows its real, private and virtual memory sizes. To check from Terminal, this read-only command prints a short summary, then the ten processes using the most memory:

top -l 1 -o mem -n 10 -stats pid,command,mem

On our Mac, part of the output read:

PID    COMMAND          MEM
171    WindowServer     2478M
46405  com.apple.Virtua 1955M
864    Safari           1912M
44761  com.apple.WebKit 1124M

top cuts names at 16 characters: com.apple.Virtua is a virtual machine's process, and com.apple.WebKit lines are web pages open in Safari or another app that uses WebKit. WindowServer, which draws the screen, is often near the top and is rarely the cause; What is WindowServer? explains when it is.

Make room for swap

Check how much space is free. This command only reads:

df -h /System/Volumes/Data

The Avail column is your free space. On our Mac it showed 7.1Gi available, 99% used, while swap stood at 18 GB: not far from this warning. Apple doesn't publish a minimum, but the more free space there is, the more room swap has. How to check storage on a Mac shows the other ways to see it and why the figures differ. How to free up space on your Mac goes through it safely, starting with the built-in tools, and What is System Data? explains the category that often hides the space.

Stop it coming back

• Update the app that grew, and macOS. Memory bugs are the kind of thing updates fix.
• Quit heavy apps when you finish with them, instead of leaving them open in the background, and close tabs you're not using.
• Keep free space on the startup disk, so swap can grow when it needs to.
• Restart now and then if one app slowly fills memory and there's no update yet.
• Plan for more memory if Memory Pressure is yellow or red most days. On Apple silicon it can't be added later; how much RAM you need helps you judge it.

For everything else about freeing memory, including why RAM cleaners don't help, see how to clear RAM on a Mac. If the Mac is slow without the warning, Why is my Mac so slow? goes through the other causes.

How Tend helps

Tend's free Memory page, in Advanced view, shows memory pressure, swap used and the apps using the most memory right now, so you can spot the app that's taking memory and quit it before macOS has to pause anything. Energy & Apps, also free, has Quit and Force Quit on every app. Tend Pro's runaway-app alert watches CPU (an app above 80% for 5 minutes), not memory, so for this problem the Memory page is the one to check.

Questions

Related guides

Sources

• Apple, View memory usage in Activity Monitor on Mac
• Apple, If your Mac runs slowly
• Apple Developer, About the Virtual Memory System (documentation archive)
• Window and button text read from macOS 27.0.1; top, df and the swap files checked on a MacBook Pro with M2 Max and 32 GB, macOS 27.0.1

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