How to free up memory on a Mac (and when not to bother)

Look at the pressure, not the number

Open Activity Monitor (in Applications › Utilities) and click Memory. Ignore the big number and look at the Memory Pressure graph at the bottom. Green means memory is being used well. Yellow means your Mac may need more room eventually. Red means it needs more memory now.

A Mac that uses nearly all its memory is doing its job: free memory doesn’t make anything faster.

What the other numbers mean

• Cached Files are files kept in memory nothing else is using, so they open faster. They make way the moment something needs the room, so a big number is fine.
• Compressed is memory macOS has squeezed to fit more in.
• Swap Used is memory moved out to the disk. A little is normal; lots of it while the graph is red means you’re short.
• Wired Memory is what macOS itself needs and can’t give up.

When it’s red: what actually helps

• Quit the apps you aren’t using, browsers with dozens of tabs first.
• In Activity Monitor, click the Memory column to sort by it, select the hungriest app, click Stop, then Quit. (Force Quit loses anything unsaved.)
• Restart now and then, so whatever has piled up starts fresh.
• Stop apps opening by themselves, in System Settings › General › Login Items & Extensions.

What doesn’t help

“Memory cleaner” apps that empty your memory by pushing everything out of it mostly make your Mac slower for a while, as it loads it all back. And the purge command only clears the disk cache; it doesn’t touch your apps’ memory.

A heads-up instead of a check-up

SideDock’s Memory tile shows what’s in use and what it’s made of, one hover away. And if your Mac really does run short, Pip tells you which app is to blame, so you don’t have to keep an eye on it.