Disclosure upfront: I make Shiny, which is a paid Mac memory cleaner at $4.99. I am not on this list. This post is specifically about free options, and I have no stake in ranking them a particular way. I'll mention Shiny briefly at the end for anyone who decides they want to pay for something, but the bulk of this post is about what costs nothing.
What does "free Mac memory cleaner" actually mean?
RAM is the temporary workspace your Mac uses to hold everything that's running. When it fills up, your Mac slows down. A "memory cleaner" reclaims that space by releasing memory that's been allocated but isn't actively needed.
The word "free" is used loosely in the Mac app space. Some apps call themselves free but show aggressive upgrade popups every few minutes. Others have a free tier that genuinely works, with paid extras you don't need. And some are completely free with no catches at all.
This list only includes options where the free tier actually does the job. If you'd need to pay to get the core feature working, it's not on here. See the full best Mac memory cleaners list for the paid options including Shiny.
Worth knowing: macOS measures memory health using "memory pressure." Open Activity Monitor, click the Memory tab, and look at the bar at the bottom. Green is fine. Yellow means your Mac is working harder to manage memory. Red means things are tight. If yours is mostly green, you probably don't need anything on this list.
The five legitimate free options ranked
macOS itself
Free, built-inWhat it does: macOS automatically manages memory in the background. It releases inactive memory, compresses memory that hasn't been used recently, and swaps to storage when things are very tight. No app required, no Terminal, no action on your part.
Why #1: Because most people searching for "free Mac memory cleaner" don't actually need one. The system is already doing the job. The question worth asking first is: is my Mac actually slow because of memory pressure? Check Activity Monitor. If the pressure is green, you're done. No app needed.
Tradeoffs: You can't trigger it manually. If your Mac has hit yellow or red pressure and you want it cleared right now rather than waiting for the system to sort itself out, you'll want one of the options below.
Best for: most Mac owners. If you haven't checked Activity Monitor yet, start here.
sudo purge (Terminal)
Free, built-inWhat it does: A Terminal command Apple has shipped with every Mac since macOS Mavericks. Open Terminal, type sudo purge, press Return, enter your password, and macOS releases its inactive memory pages. The effect is visible in Activity Monitor within a few seconds.
Why #2: It's legitimate, free, and does exactly what most paid memory cleaners do under the hood. If you're comfortable opening Terminal occasionally, this is all you need. No download, no install, no app living in your menu bar using memory to save you memory.
Tradeoffs: Terminal is intimidating if you've never used it. On Apple Silicon Macs (M1, M2, M3, M4) the effect is smaller than on older Intel Macs because the memory architecture is more efficient. The impact is real but modest. Also, you have to do it manually every time.
Best for: anyone comfortable with Terminal who wants a one-time free solution with no apps involved.
OnyX (Titanium Software)
Free, donationwareWhat it does: A Mac maintenance toolkit that has been continuously updated since 2003. Includes maintenance scripts, cache clearing, hidden preference toggles, and memory management. The Maintenance tab includes options to run Unix maintenance scripts and clear system caches, which frees up memory and disk space together.
Why #3: Titanium Software is a respected indie developer with a track record most Mac apps can't match. OnyX is completely free with a donation option, no popups, no upgrade pressure, no telemetry. It's the gold-standard free maintenance app for Mac. If you want more than just memory (caches, scripts, disk maintenance), OnyX gives you a lot for nothing.
Tradeoffs: The UI is dated and can be overwhelming for non-technical users. There's no one-click button in a menu bar. You have to open the app, find the right tab, and run the right script. Not the right fit if you want something simple and quick. Also: you must download the version that matches your macOS version exactly. Check the Titanium Software website before downloading.
Best for: users who want a free all-round maintenance toolkit and don't mind spending a few minutes learning the interface.
Memory Cleaner (Nektony)
Free tier availableWhat it does: A menu-bar app that shows your current RAM usage and provides a one-click clean button. The free tier monitors memory in real time and lets you trigger a clean on demand. The paid upgrade adds auto-clean by threshold and CPU monitoring, but those aren't necessary for most users.
Why #4: Nektony is a legitimate software company with other well-regarded Mac apps. The free tier is genuinely useful, not crippled. You get the core feature (see your memory use, click to clean) at no cost. If the idea of typing sudo purge in Terminal doesn't appeal, this is the friendliest free alternative.
Tradeoffs: There are upgrade prompts when you open the full app, though they're not aggressive. Some telemetry is enabled by default. The UI is more cluttered than minimal apps. The free tier doesn't auto-clean; you have to trigger it manually. For automatic cleaning, you'd need the paid tier or a different approach.
Best for: users who want a simple menu-bar app with a one-click clean button and no Terminal involved.
Memory Diag (Rocky Sand Studio)
Free tier availableWhat it does: A menu-bar app with a colour-coded memory pressure graph. It shows you how your RAM usage trends over time, which is more informative than a single snapshot. The free tier includes the graph and a basic clean button. The Pro tier adds customisation options, but the free tier covers most users' needs.
Why #5: The visualisation is genuinely good. If you want to understand your memory situation rather than just react to it, watching the pressure graph over a working day tells you a lot. You'll see which apps cause spikes, when things get tight, and whether cleaning actually helps or whether the pressure just comes back.
Tradeoffs: The cleaning action wraps sudo purge more than anything else, so it's less aggressive than apps that also close orphaned processes. Memory Diag is more of a monitor than a cleaner. The free tier is useful but the app's strength is the graph, not the cleaning. If you mainly want to watch memory rather than aggressively manage it, this is the one.
Best for: users who want to visualise memory pressure trends and understand what's causing slowdowns.
When free is enough
Free is enough for most people. If your Mac is running fine and you're just curious about memory cleaners, the honest answer is: you don't need one. macOS is doing the job already.
Free is also enough if you only occasionally notice slowdowns. Open Activity Monitor, check the memory pressure, and if it's yellow or red, run sudo purge in Terminal or click clean in Memory Cleaner. Job done. No ongoing cost, no background process sitting in your menu bar.
Where free starts to feel limited is when you want something passive. If you'd rather not think about memory at all, and you'd prefer an app that handles it quietly in the background without popups asking you to upgrade, the free tier of any of these apps won't quite get you there. That's the gap paid apps fill.
For more context on whether a memory cleaner is worth it for your situation, see are Mac cleaner apps actually worth it and how to free up RAM on Mac.
When you might outgrow free
A few situations where free tools start to feel like friction:
- You want something that cleans automatically without you triggering it.
- You want a clean one-tap experience with no upgrade prompts anywhere in sight.
- You use multiple Macs and want the same tool on all of them.
- The menu-bar UI of free apps feels cluttered and you'd prefer something minimal.
If any of those describe you, the paid tools are worth a look. The cheapest legitimate option is Shiny at $4.99 once for up to three Macs. The price is low enough that the comparison isn't really "free vs Shiny." It's more: "Is a one-time $4.99 worth removing the friction?" For some people that's an easy yes. For others the free options work fine. Both are honest answers.
Free works for most users. If you outgrow it, Shiny is the simplest paid step at $4.99 once.