Not in the way they suggest. A memory cleaner makes the “free memory” number jump, which feels like something happened. Within a minute or so the number drifts back, and your Mac is no faster. In the meantime it may have been slower.
What a cleaner actually does
macOS fills spare memory with cache: files and data it expects to need again. Cleaners empty that cache, either by running macOS’s own purge tool or by briefly claiming a large block of memory so macOS has to give the cache up. Either way, free memory goes up because useful data was thrown away.
Why it doesn’t last
Your apps still need what was in that cache. They read it back from disk, which is slower than reading it from memory, and the free figure falls back to where it was. You pay for the bigger number with a burst of disk reads.
Why it doesn’t make a slow Mac faster
Cache is the first thing macOS drops when an app needs memory, instantly and for free. So a large cache was never what was slowing your Mac down. What does is memory pressure: apps together needing more memory than there is, which forces macOS to compress and swap. A cleaner doesn’t change what your apps need, so memory pressure barely moves.
What helps instead
- Close what’s holding memory. Activity Monitor’s Memory tab, sorted by memory, shows which apps they are.
- Restart an app that keeps growing. A leak only lets go when the app quits.
- Free up disk space, so swapping has room when it does happen.
- Update apps running under Rosetta, which use more memory and CPU than native ones.
Each of these changes what your Mac actually needs, so the improvement lasts. The full list of causes, and how to check each.
So is the free memory number useless?
On its own, mostly. Little free memory with green memory pressure is a healthy Mac making good use of its RAM. Plenty of free memory with red pressure is very rare. Watch pressure and swap, and let macOS manage the cache.