Swap is memory macOS has moved from RAM onto the disk. When apps need more memory than your Mac has, macOS first compresses what’s in RAM. When compressing isn’t enough, it writes the parts you’re least likely to need soon to swap files on the startup disk, and reads them back when an app asks for them.
Some swap is normal, even on a Mac with plenty of RAM. It becomes a problem when it keeps growing while memory pressure stays high, because reading memory back from disk is far slower than reading it from RAM. That’s where the beachball comes from.
Where to see it
Open Activity Monitor and choose the Memory tab. At the bottom, Swap Used shows how much is on the disk now, next to the Memory Pressure graph. In Terminal:
sysctl vm.swapusageThe swap files themselves are in /System/Volumes/VM, added 1 GB at a time. They count towards System Data in Storage settings.
How much swap is too much?
There’s no official figure. The amount matters less than what’s happening alongside it:
- Swap of a few GB, memory pressure green: fine. macOS moved out memory nobody was using. It may sit there for days.
- Swap growing through the day, pressure yellow: your Mac is short of memory for what you keep open. You’ll notice pauses when switching apps.
- Swap growing fast, pressure red: macOS is swapping constantly. Expect beachballs and tabs that reload.
Read what memory pressure means for how the graph works.
“Your system has run out of application memory”
This dialog appears when macOS can’t make more room: memory is full and swap can’t grow, usually because the disk is nearly full. Quit something from the list it shows, then free up disk space so swap has room. See how to free up space safely.
How to bring swap down
- Quit what you aren’t using. In Activity Monitor’s Memory tab, sort by Memory. Quit the apps at the top that you don’t need right now, with Command-Q rather than closing the window.
- Look for an app that keeps growing. An app whose memory climbs hour after hour while you use it the same way is leaking. Quitting and reopening it gets the memory back.
- Keep free disk space. Swap needs room to grow. Below about 10% free, swapping turns into stalls.
- Restart. Swap is cleared completely at restart. macOS shrinks it on its own too, but slowly, so the figure may stay high for a while after you quit apps.
Does swap wear out the SSD?
Every gigabyte swapped is written to the SSD, and SSDs are rated for a certain amount of writing. Normal swapping uses a small part of that over the life of a Mac. Heavy swapping every day, on a Mac with too little memory for its workload, wears it faster. See how to check your SSD’s health.
What doesn’t help
- Turning swap off. macOS doesn’t let you, for good reason: without it, apps would be force-quit when memory runs out.
sudo purgeand RAM cleaners. They clear the disk cache, not swap, and your Mac reads that data back straight away. See why RAM cleaners don’t work.
Unslow shows memory pressure in the menu bar, records when your Mac slowed down from swapping, and names the apps that were holding the memory at the time.