“Your system has run out of application memory”

What the warning means

macOS treats memory as a layered system. Apps first use RAM (on Apple-silicon Macs, the unified memory built into the chip). When RAM gets full, macOS compresses memory that hasn’t been used recently. When that isn’t enough, it moves less active memory into swap space on your startup disk.

The full message reads “Your system has run out of application memory. To avoid problems with your computer, quit any applications you are not using.” It comes with a Force Quit Applications window. By the time you see it, all three layers are under strain. Your Mac is asking you to choose what to close because it can’t safely keep everything open.

Two situations cause most cases:

• One app keeps asking for more memory. This is often called a memory leak: an app uses memory and doesn’t give it back when it’s done, so its total keeps rising while you work. Browsers with many tabs, long-running development servers, and some creative apps are common places to look.
• The startup disk is nearly full. Swap lives on your startup disk. With very little free storage, macOS has less room to move memory out of RAM, so the warning can appear sooner.

What to do right now

1. Save your work

   Switch to any app with unsaved documents and save with ⌘S. Quitting normally gives apps a chance to save; force quitting doesn’t.

2. Quit apps you aren’t using

   Use ⌘Q in each app, or choose Quit from its menu. Start with apps you forgot were open. Closing a window often leaves the app running, so quit the app itself.

3. Check the Memory tab in Activity Monitor

   Open Activity Monitor (Applications → Utilities), click Memory, and click the Memory column to sort by size. The largest entries are where quitting will help most. Browser helpers such as Google Chrome Helper (Renderer) belong to the browser, so quitting the browser closes them too.

4. Force quit only what won’t respond

   If an app ignores ⌘Q, use the Force Quit Applications window that appeared with the warning. You may lose unsaved changes in that app. See how to force quit on a Mac for the other options.

5. Restart if things stay slow

   If the Memory Pressure graph stays red after you quit apps, restart from the Apple menu. A restart gives macOS and every app a fresh start.

How to find the cause

If the warning comes back, the goal is to find the one thing that grows. A few checks narrow it down.

• Watch one app over time. Leave Activity Monitor’s Memory tab open while you work. An app whose number rises steadily and never drops, even when you stop using it, is the likely cause. Quitting and reopening it should bring it back down.
• Look at the bottom of the Memory tab. Memory Pressure summarizes how well RAM is keeping up. Green is fine, yellow means your Mac might eventually need more RAM, and red means it needs more right now. Swap Used shows how much is on disk. A large swap number with red pressure fits this warning.
• Check free storage. Open System Settings → General → Storage. If the startup disk is nearly full, move or delete large files you don’t need. Apple lists low disk space as a common cause of a slow Mac.
• Think about what you started recently. A new app, an update, a browser extension, or a dev server you left running yesterday are all worth checking.

For a closer look at the numbers in the Memory tab, read how to check CPU and memory usage on a Mac.

What doesn’t help

Memory “cleaner” apps promise to free RAM with one click. macOS already manages memory, and unused RAM doesn’t make your Mac faster. Apple’s own guide notes that having unused memory doesn’t necessarily improve performance. If a cleaner forces macOS to drop cached files, apps simply load them again. Quitting the app that is actually growing does more. Our page on memory cleaners goes into more detail.

macOS manages swap on its own, so there’s nothing to tune there. Free disk space and fewer large apps open at once are what give it room to work.