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"Your system has run out of application memory"

This dialog is not usually telling you to buy more RAM. It is telling you that macOS ran out of room to put things — and there are two different reasons for that, with two different fixes.

Last updated August 29, 2026 · by the RAMKeeper team

The warning appears with a list of running apps and a Force Quit button, and it usually arrives at the worst moment. Before force-quitting anything: this message does not mean your RAM is full. macOS is comfortable running with almost no free RAM. It means macOS tried to make room and could not.

Deal with it right now

If you are staring at the dialog and need your work back, in this order:

1. Read the list in the dialog before clicking anything. It is sorted by memory use. The app at the top is the suspect — note its name, you will want it in a moment.
2. Save what you can in other apps first. The dialog is modal but the system is usually still limping along. Command-S in your editor buys you more than a fast force quit does.
3. Force quit the top item, not the one you care least about. The instinct is to close something safe. That frees a little and the dialog comes back in five minutes.
4. If the top item is your work, quit it normally instead. Switch to it and press Command-Q. A normal quit gives it a chance to save; a force quit does not.

Then find out which of the two causes it was

The dialog has one message but two quite different root causes, and they need opposite responses.

Cause 1: your startup disk is nearly full

This is the one people miss, and it is common. When RAM fills up, macOS writes cold pages to a swap file on the startup disk. Swap needs free disk space to grow. If the disk has nothing left to give, macOS has run out of both places to put memory — and that is precisely the condition that produces this dialog.

This is why a Mac with 32 GB of RAM and a full disk can throw an out-of-memory error while a 16 GB Mac with a half-empty disk never does.

Check it: → About This Mac → More Info → Storage. If you are under roughly 10–15 GB free, fix that first and see whether the problem disappears. No amount of app-quitting will help while the disk is the real constraint.

You can also see both numbers from Terminal:

df -h /              # free space on the startup disk
sysctl vm.swapusage  # how much swap is in use right now

For reference, here is a healthy pair from a working machine:

Cause 2: one process is growing without limit

If the disk has plenty of space, then something is consuming memory faster than macOS can reclaim it. In practice this is nearly always a single process, not "too many apps open".

The usual suspects, in rough order of how often they are responsible:

• A browser with a runaway tab. One page with a leaking script can take tens of gigabytes. In Chrome, its own Task Manager (Window → Task Manager) names the tab.
• Electron apps left running for weeks — chat and AI desktop clients are the common ones. They often grow slowly enough that you never notice until the dialog appears.
• Mail, Photos, or a sync client mid-reindex. Usually temporary, but it can be enormous while it lasts.
• A genuine leak in one app after a recent update.

The tell is the shape, not the size: an app that has been at 4 GB all day is fine, an app that was at 400 MB this morning and is at 12 GB now is your answer.

How to confirm it, rather than guess

1. Open Activity Monitor (Applications → Utilities) and click the Memory tab.
2. Click the Memory column heading to sort by size, largest first.
3. Watch the Memory Pressure graph at the bottom, not the "Memory Used" figure. Apple defines pressure from "the amount of free memory, swap rate, wired memory, and file cached memory" — it is the one reading that reflects whether the machine is actually struggling.
4. Leave it open for a few minutes while you work. The process whose number climbs steadily is the one to act on.

One caveat worth knowing: browsers and Electron apps show up as a wall of helper and renderer processes rather than one line, so the true cost of "Chrome" is spread across dozens of rows. Chrome's built-in Task Manager groups them properly, and so does any tool that rolls helpers up under their parent app.

What not to do

• Do not install a memory cleaner in response to this dialog. The techniques those apps use — flushing the disk cache, allocating and releasing a large block — do not create the thing you are short of, and one of them makes the machine slower. We went through what each technique does, with measurements, in do Mac memory cleaners actually work?
• Do not force quit down the list at random. You will lose unsaved work in something innocent and the real culprit will still be running.
• Do not assume you need more RAM yet. If the cause was a full disk or one leaking app, more RAM would only have delayed the same dialog.

Stopping it from happening again

1. Keep 10–15% of the startup disk free so swap always has somewhere to go.
2. Restart the known offender on a schedule. If one chat or AI client is always the top of the list, quitting and reopening it once a day costs seconds and removes the problem.
3. Restart the Mac occasionally. Not folklore in this case — it is the bluntest way to clear an accumulating leak.
4. Watch memory pressure, not free RAM. Green is fine no matter how little is free. Sustained red is the signal.
5. Consider whether the RAM is genuinely undersized only after the first four. If pressure sits in the yellow-to-red band during ordinary work with no single app misbehaving, that is the real case for more memory — and on Apple silicon that means the next Mac, so it is worth being sure.