Fix "Mac Out of Application Memory" Errors

In short: The "Your system has run out of application memory" alert usually means RAM is full and your startup disk is too crowded to help. Here is what is really happening and how to clear it safely, without deleting anything you can't get back.

You are working along and a gray alert stops everything: Your system has run out of application memory. macOS asks you to force-quit apps to keep going. It looks alarming, but it is a solvable problem, and you rarely need to buy more RAM to fix it. This guide walks through what the message means and the exact steps to clear it on macOS Sonoma and Sequoia.

What the message actually means

Your Mac uses two kinds of storage to keep apps running: physical RAM (fast) and swap space on your startup disk (slower). When RAM fills up, macOS quietly moves the least-used data to a swap file on disk. That normally works fine. But when your startup disk is also nearly full, there is nowhere to put the swap, so macOS runs out of room to juggle everything and shows the application memory warning.

So this is usually two problems at once: too much loaded into memory, and too little free space on the disk that backs it up. Fixing both is what makes the warning stop coming back.

Step 1: Find and quit the memory hogs

Open Activity Monitor (press Command-Space, type Activity Monitor, press Return). Click the Memory tab, then click the Memory column header once or twice so the biggest users sort to the top.

• Look at the Memory Pressure graph at the bottom. Green means you are fine; yellow or red confirms your Mac is under real pressure.
• Web browsers with dozens of tabs are common culprits, along with photo and video editors, virtual machines, and anything left running for days.
• To close one, select it and click the X button (or the octagon-stop icon) in the toolbar, then choose Quit. Use Force Quit only if a normal quit does nothing.

Save your work first. Force-quitting an app skips its normal save prompts, so close documents the polite way when you can.

Step 2: Restart to reset swap and caches

If the warning is already on screen and apps are frozen, the cleanest reset is a restart. Choose Apple menu > Restart. A reboot clears swap files, releases leaked memory, and flushes temporary caches that pile up during long uptimes. If you routinely go weeks without restarting, a fresh start alone often ends the warnings for a while.

Step 3: Free up disk space so swap has room

This is the step most people skip, and it is often the real fix. Check your free space in Apple menu > System Settings > General > Storage. If your startup disk is above roughly 90 percent full, macOS has little room for swap. Aim to keep at least 10 to 15 percent free.

Safe places to reclaim space, in order of least risky first:

1. Empty the Trash. Files sitting in the Trash still occupy the disk until you empty it.
2. Clear Downloads. Old installers and disk images (.dmg files) collect here and are rarely needed twice.
3. Remove large files you no longer need. In the Storage screen, use Documents and the built-in recommendations to spot big items.
4. Clear user caches. Apps rebuild these automatically. You can review the ~/Library/Caches folder, but move items to the Trash rather than deleting outright so you can restore anything an app misses.

Do not go poking inside the /System folder. macOS protects it for good reason, and nothing you need to clean lives there.

A quick word on safe cleaning

Whatever tool or method you use, the safe pattern is the same: preview what will be removed before you commit, stick to user-level junk (caches, logs, Trash) by default, and send removals to the Trash so they are reversible. If clearing a cache causes an app to misbehave, you just pull the folder back out of the Trash. Permanent deletion has no undo, so avoid tools that skip the Trash.

Privacy matters here too. A disk cleaner has no reason to send your file list anywhere, so it should not phone home. If you want to verify that for yourself, run a firewall like Little Snitch and watch whether the app makes outbound connections while it scans.

If it keeps happening

Persistent warnings on a Mac that is not low on disk usually point at one runaway app with a memory leak. Use Activity Monitor to catch which process climbs steadily over minutes, then update or reinstall that app. Keeping macOS current also helps, since Apple regularly fixes memory bugs in point releases.

If you would rather automate the disk cleanup part, a good cleaner makes freeing space quick without risking your data. Our top free pick is CoreSweep: free forever, with an optional one-time Pro upgrade ($49), zero telemetry, and every removal sent to the Trash so it stays reversible. A strong best-value runner-up is SkoonMac, which is also free with a one-time Pro at just $19. Either one lets you preview first and clean only user-level junk, which is exactly the habit that keeps the application memory warning from coming back.

Frequently asked questions

What does "Your system has run out of application memory" mean on a Mac?

It means your RAM is full and macOS has nowhere left to offload data. macOS normally moves the least-used memory into a swap file on your startup disk, but when that disk is also nearly full there is no room for swap, so the warning appears. It is usually two problems at once: too much loaded into memory and too little free disk space.

Do I need to buy more RAM to fix the out of application memory error?

Usually not. Most of the time the fix is quitting memory-hungry apps in Activity Monitor, restarting to clear swap and caches, and freeing up disk space so swap has room to work. Buying more RAM only helps if you genuinely run heavy workloads and the warnings continue after your disk has plenty of free space.

Is it safe to clear caches to fix the memory warning?

Yes, if you do it carefully. Stick to user-level junk like the Trash, Downloads, and ~/Library/Caches, and move items to the Trash rather than deleting them outright so anything an app misses can be restored. Never touch the /System folder, and avoid tools that permanently delete files instead of using the reversible Trash.

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