Mac says "Your system has run out of application memory"

Why it happens

Every open app and tab takes some memory. When they need more than your Mac has, it borrows space on the drive, called swap, which is much slower. If one app keeps grabbing more, or the drive is too full for swap, your Mac runs out and shows this message.

How to fix it

1. In the message itself, look at the list of apps. Anything showing many gigabytes, often a browser, is the likely cause. Select it and click Force Quit if it has stopped responding. Otherwise, switch to it, save your work and quit it with Command-Q.

2. Close browser tabs you aren't using. Each tab can use as much memory as a small app.

3. Press Command-Space, type Activity Monitor and press Return. Click Memory, then the Memory column heading so the biggest users are at the top.

   Activity Monitor›Memory

4. Look at the Memory Pressure graph at the bottom. Green is fine. Yellow means your Mac is working hard, and red means it needs more memory than it has. Quit the largest items you don't need until it turns green.

5. Restart your Mac once you've saved everything. That gives every app a fresh start.

Still not fixed?

1. Check your free space in General > Storage. Swap needs room on the drive, so a nearly full disk can trigger this message even with only a few apps open.

   General›Storage

2. If one app grows bigger and bigger until the message appears, it may have a bug. Update it, and if it keeps happening, contact the app's maker.

3. Remove apps you don't need from Open at Login so they don't use memory in the background.

   General›Login Items & Extensions›Open at Login

4. On Macs with Apple silicon, memory is part of the chip and can't be added later. If Memory Pressure is red with your normal work, your next Mac needs more memory.

5. If the message appears with almost nothing open, plenty of free space and after a restart, contact Apple Support. That's not normal and worth a proper check.