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How to free up RAM on your Mac
Almost every guide on this topic starts from a false premise: that unused RAM is good and full RAM is bad. On macOS the opposite is true. Empty memory is wasted memory, and the system deliberately fills it with file caches and compressed pages to make everything faster. What you actually want is low memory pressure and little or no swap. This page shows you how to read those numbers, what genuinely helps when they are bad, and why the popular tricks mostly do not.
Updated 2026-08-02 · Written by the CleanerMac team · macOS 13–15 tested
Read the right number in Activity Monitor
Open Activity Monitor from Applications → Utilities and switch to the Memory tab. Ignore the headline "Memory Used" figure entirely. Four things below it tell the real story.
- Memory Pressure — the graph at the bottom left. Green means macOS is comfortable, even if RAM looks full. Yellow means it is working to compress and evict pages. Red means it cannot keep up and performance is genuinely suffering.
- Swap Used — how much memory has been written out to the SSD. A few hundred megabytes after a long session is normal. Several gigabytes, climbing steadily, is the clearest sign you are short of RAM.
- Compressed — memory macOS has squeezed rather than swapped. This is the system working as designed and is far cheaper than swap. A large compressed figure with green pressure is fine.
- Cached Files — file data kept in RAM because there was nothing better to do with it. This is instantly reclaimable and is the main reason "free RAM" looks alarmingly low.
The practical rule: green pressure means do nothing. Yellow with rising swap means act. Red means act now.
What genuinely reduces memory pressure
- Quit the biggest consumers. Sort the Memory tab by the Memory column and look at the top five. It is almost always a browser, a chat app built on a web framework, a virtual machine or a container runtime. Quitting one app usually solves the whole problem.
- Close browser tabs and windows. Each tab is a separate process holding its own heap. A hundred open tabs can account for many gigabytes on their own, and browser tab-suspension features exist precisely for this.
- Restart. Long uptimes accumulate leaks that no amount of cleaning will recover. If your Mac has been awake for weeks, restart before doing anything else.
- Check for a runaway process. A single misbehaving helper can consume memory without limit. Sort by Memory, and if one process is far ahead of everything else and growing, quit it and see whether it returns.
- Reduce login items. Fewer background processes means more headroom permanently, not just after a purge. Trim them in System Settings → General → Login Items & Extensions.
- Free disk space. Swap lives on the startup volume. When the disk is nearly full, macOS has nowhere to page out to and memory pressure turns into system-wide stalling. If you are near capacity, see how to free up space on a Mac and startup disk full first.
About the purge command
You will see sudo purge recommended constantly. Here is what it actually does: it flushes the file-system cache and forces macOS to release inactive pages, so the "free" number in Activity Monitor jumps up dramatically.
What it does not do is make your Mac faster. The memory it frees was working for you as a disk cache. Immediately after running it, files must be re-read from storage, so for the next few minutes the machine can feel slower than before. macOS refills those caches within moments, so the impressive-looking free-memory number does not last either.
It is still a legitimate tool for two jobs: producing a clean baseline before benchmarking, and confirming whether a slowdown is caused by memory pressure or by something else. Used that way it is useful. Used as routine maintenance it is theatre — and any app that presents a memory purge as its headline speed feature is selling you a number, not a result.
Understanding "Your system has run out of application memory"
This dialog appears when macOS cannot allocate more memory and cannot swap further, usually because the startup disk is full or a process is leaking badly. The dialog lists applications and offers to force-quit them.
- Force-quit the largest listed app first — that is normally enough to recover control.
- Then check free space in Apple menu → System Settings → General → Storage. If the disk is nearly full, that is the actual cause; swap could not grow.
- Check Activity Monitor for a process with an implausible memory figure. A leak in a single app produces this dialog on machines with plenty of RAM.
- If it happens repeatedly with no obvious culprit, restart in Safe Mode (Apple Silicon: hold the power button at startup, choose the disk, hold Shift and click Continue in Safe Mode) to rule out third-party login items.
What does not work
| Claim | Reality |
|---|---|
| "Free up RAM for a faster Mac" | Freeing cached memory removes a performance optimisation. Pressure, not free RAM, is what matters. |
| "RAM booster apps that run continuously" | A resident process consuming CPU and memory to report on memory is a net loss. |
| "Disable swap for speed" | Swap is a safety valve. Disabling it turns a slowdown into a crash, and requires disabling SIP. |
| "Clearing caches frees RAM" | Disk caches and RAM are different things. Clearing ~/Library/Caches reclaims storage, not memory. |
| "More RAM always fixes it" | Often true, but a single leaking app will exhaust any amount. Diagnose before you buy. |
Apple Silicon changes the maths
M-series Macs use unified memory shared between CPU and GPU, on a very fast bus, with an extremely fast SSD behind it. The practical effect is that an Apple Silicon Mac tolerates memory pressure far better than an Intel Mac with the same nominal RAM — swapping is quick enough that moderate pressure often goes unnoticed.
That is not a reason to ignore the numbers. Sustained heavy swapping still writes a lot of data to the SSD, and 8 GB configurations do hit walls with video editing, large Xcode projects, virtual machines and dozens of browser tabs. Note also that GPU-heavy work consumes the same pool, so a demanding graphics task reduces what is available to everything else.
Keeping memory healthy without thinking about it
- Restart weekly. It is the single most effective memory habit there is.
- Keep 10–15% of the startup disk free so swap always has room.
- Audit login items twice a year; background helpers accumulate silently.
- Use browser tab groups or a suspender extension instead of leaving everything open.
- Quit virtual machines and container runtimes when you finish, rather than leaving them idling.
CleanerMac fits into this as a convenience rather than a miracle: its Tune-Up tab exposes the memory purge as a button for the times you genuinely want it, alongside the DNS flush, Quick Look reset and Finder/Dock restart, and its status widget shows current pressure so you can tell whether acting is even warranted. It is deliberately honest about the limits — no tool can create RAM, and anything claiming otherwise is inventing a number. For the storage side of the same problem, which is often the real bottleneck, start with clearing caches safely and finding large files, and for the whole picture see how to speed up a slow Mac.
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Frequently asked questions
Is it bad if my Mac's memory is almost full?
No. macOS intentionally uses spare RAM for file caching and compressed pages, so a nearly full memory graph is normal and healthy. Judge by the Memory Pressure graph and Swap Used figure in Activity Monitor instead. Green pressure means there is nothing to fix.
Does sudo purge actually free RAM?
It does free inactive and cached memory, so the free-memory number jumps. But that memory was serving as a disk cache, so the Mac can feel slower for a few minutes afterwards while caches rebuild. It is a diagnostic tool, not routine maintenance.
How much swap is too much on a Mac?
A few hundred megabytes is unremarkable. Several gigabytes that keeps climbing during normal use means you are genuinely short of RAM for your workload. Combined with yellow or red memory pressure, that is the point to close apps or consider more memory.
Why does my Mac say it has run out of application memory?
Either a process is leaking memory or the startup disk is too full for swap to grow. Force-quit the largest app in the dialog, then check free space under System Settings, General, Storage. If it recurs, look for one process with an implausible memory figure in Activity Monitor.
Is 8 GB of RAM enough on an Apple Silicon Mac?
It is comfortable for browsing, office work and light photo editing thanks to fast unified memory and a very fast SSD. It becomes limiting with video editing, virtual machines, large Xcode projects or heavy tab use. Check your own memory pressure over a normal working day before deciding.
Do memory cleaner apps help?
Not the ones that run continuously in the background, since they consume the resource they claim to protect. A purge button you press deliberately is fine for diagnostics. The real fixes are quitting heavy apps, restarting regularly and keeping the disk from filling up.