Memory · an honest answer
Does purging RAM actually do anything?
Almost nothing. The figure jumps because the disk cache was thrown away — and macOS reads that cache straight back, so you paid for it twice.
What the button empties
macOS fills otherwise-idle memory with recently read file data. That cache is not memory being used up: the moment an app needs the room, the system drops the cache itself, without being asked and without slowing anything down. A purge just does it early, and the next time those files are wanted they are read from disk again.
So the number on screen improves and the machine does not. If anything it is briefly slower, because everything the cache was holding has to be fetched back.
The same machine, measured three ways
RefreshYourMac reads these from the kernel's own memory statistics rather than estimating them:
- 40.6 MB genuinely spare — pages nothing wants, which a purge would free for real.
- 3.12 GB of file cache — freed by a purge, and read straight back.
- 4.83 GB held by the compressor — which a purge cannot touch at all.
That last line is the one worth keeping. On this Mac the compressor was holding 18.09 GB held in 4.83 GB: real data belonging to running apps, squeezed down about three and a half times. It is why free memory reads so low on a healthy Mac, and no button moves it.
What to watch instead
- Memory pressure, which is what macOS itself acts on. Green means there is no problem to solve, whatever the free-memory figure says.
- Swap activity — pages moving to and from disk right now. A number that is actually zero most of the time, and the one that means something when it is not.
- The compression ratio, which tells you how hard the system is working to keep everything resident.
Does the command exist?
Yes — /usr/sbin/purge ships with macOS, and the cleaners that offer this button are wrapping it. RefreshYourMac does not, and shows you those three numbers where the button would have been, so the refusal is something you can check rather than something you have to believe. The readings, and the list of apps actually holding your memory, are on CPU and memory. For the fixes that do make a slow Mac faster, see how to speed up a Mac.
A purge will not clear macOS’s out-of-memory alert either; see what to do when the system runs out of application memory.
What to do next: see these numbers for your own Mac. Download RefreshYourMac free, or get it on the Mac App Store.
What it costs to have an app do this
| RefreshYourMac | CleanMyMac | MacKeeper | |
|---|---|---|---|
| Pay once | $24.99 | €119.95 on MacPaw’s store; $89.99 for CleanMyMac X on the Mac App Store | subscription only |
| Yearly | $14.99 a year, first 7 days free | $39.99/yr on the Mac App Store; €39.95/yr on MacPaw’s store | €71.40 for the first year, 1 Mac. Their page shows it against a €119.40 list price |
| Monthly | $1.99 a month | $9.99/mo | €10.95/mo |
| Account needed | No | Yes | Yes |
Before you pay anything, both versions give you 3 free scans. CleanMyMac and MacKeeper prices read from their own pages and the Mac App Store on 27 October 2026; the full comparison is at RefreshYourMac vs CleanMyMac and MacKeeper.
Frequently asked questions
Why does my Mac show so little free memory?
macOS fills otherwise idle memory with recently read file data, and drops that cache itself the moment an app needs the room. The compressor also holds real data belonging to running apps, squeezed down. That is why free memory reads so low on a healthy Mac.
What should I watch instead of free memory on a Mac?
Memory pressure, which is what macOS itself acts on: green means there is no problem to solve. Then swap activity, the pages moving to and from disk right now, and the compression ratio, which shows how hard the system is working to keep everything resident.
What does the purge command do on a Mac?
/usr/sbin/purge ships with macOS and empties the file cache held in memory, so the free-memory figure jumps. The next time those files are wanted they are read from disk again, so the Mac can be briefly slower, and memory held by the compressor is not touched at all.