Disclosure first, since Shiny is on the list: this is a THEODOREHQ product, so the inclusion is not impartial. The rankings have been written the way a buyer would want them written. Where another app legitimately wins, this post says so. If a different memory cleaner is the right fit for you, you'll find it here.
What does a memory cleaner actually do?
A "memory cleaner" frees up RAM (the temporary workspace your Mac uses to hold what's running) when it's getting tight. The legitimate ones do three things: close orphaned helper processes (small bits of an app left over after you quit), ask macOS to release inactive memory pages it's still holding "just in case", and pause apps that have been idle for hours but are still hogging memory.
The illegitimate ones run sudo purge in a loop and show you a dramatic number. Avoid those.
For more on how memory works on Mac, see what memory pressure means.
How I ranked these
Five criteria, in this order:
- Does it actually work? (Tested on a 16 GB M2 MacBook Air running Sequoia.)
- How honest is it? No fake numbers, no scareware popups, clear about what it does and doesn't do.
- Pricing model. One-time payment beats subscription, all else equal.
- Footprint. A memory cleaner that uses 200 MB of memory itself is bad comedy.
- Privacy. Telemetry-zero is preferred.
The 5 legitimate Mac memory cleaners (2026)
Shiny
$4.99 onceWhat it does: Lives in your menu bar. One click closes orphaned helper processes, releases inactive memory, pauses apps idle for hours. Shows you what it freed.
Why #1: Cheapest legitimate option, no subscription, zero telemetry, three-Mac coverage out of the box, no popups, no upsells. Single-purpose so the entire app is the memory cleaner.
Tradeoffs: A small operation, so you're not getting a 17-year-old company's depth of polish. No malware scanner, no uninstaller, no disk view. If you want those, see #5.
Best for: people who only want a memory cleaner, hate subscriptions, and care about privacy.
Memory Cleaner (Nektony)
Free + paid extrasWhat it does: Menu-bar memory monitor with a free one-click clean button. Paid upgrade adds auto-clean by threshold and CPU monitoring.
Why #2: Free tier is genuinely useful, and Nektony is a real software company with other reputable apps. Auto-trigger by threshold (paid only) is a feature Shiny doesn't have.
Tradeoffs: Free tier is limited; paid upgrade adds up if you have multiple Macs. Some telemetry by default. UI is more cluttered than Shiny's.
Best for: people who want auto-clean by threshold, or who want to start free.
Memory Diag (Rocky Sand Studio)
Free + Pro tierWhat it does: Colour-coded memory pressure graph in your menu bar, plus a "purge" button. Pro tier adds customisation.
Why #3: The graph is excellent, more visually informative than most competitors. If you like seeing trends over time, this is your tool. The free tier covers most needs.
Tradeoffs: The cleaning action itself is light (mostly wraps sudo purge). For genuine memory relief, Shiny or Memory Cleaner do more. Memory Diag is more "monitor" than "cleaner".
Best for: people who want to watch memory pressure visually rather than just act on it.
OnyX (Titanium Software)
Free (donationware)What it does: Mac maintenance toolkit. Includes maintenance scripts, cache clearing, hidden preference toggles. Memory cleaning is buried in the Maintenance tab.
Why #4: Free, fully featured, made by a respected indie since 2003. If you want a maintenance toolbox in addition to memory clearing, OnyX is the gold standard.
Tradeoffs: The UI is dated and intimidating for non-technical users. There's no menu-bar one-click. You have to open the app and navigate to the right tab. Not the right fit if you just want a button.
Best for: power users who want a free maintenance toolkit and don't mind the UI.
CleanMyMac (MacPaw)
~$40 / yearWhat it does: Full Mac-maintenance suite. Memory cleaner is one of about a dozen features (also: malware scanner, app uninstaller, disk visualisation, junk cleanup, large file finder).
Why #5: Mature, well-supported, made by a 17-year-old company. If you want one app that handles everything Mac-maintenance-related, it's the most polished option.
Tradeoffs: Subscription model. "Smart Care" popups. The price is high if you only want the memory cleaner. Paying $40/year for what costs $4.99 once elsewhere doesn't make sense unless you'll genuinely use the breadth.
Best for: people who want a full Mac-maintenance suite and are happy with a subscription.
What about MacKeeper, MacBooster, and the others?
Three apps I deliberately didn't list because I don't recommend them:
MacKeeper has a long history of aggressive scareware-style marketing and was widely flagged as a "potentially unwanted program" for years. The company (now Clario) has cleaned up its act, but the brand reputation is hard to undo.
MacBooster (IObit) comes from a company with a controversial reputation in the Windows ecosystem. Better alternatives exist.
"Smart Mac Care", "Mac Optimizer Pro", and similar PCVark / Trend Micro apps have a long history of being flagged by reviewers for pushy upsells and exaggerated claims. Avoid.
What about just running sudo purge?
It's a free Terminal command Apple has shipped since macOS Mavericks. It releases the inactive parts of memory the system is still holding. On modern Apple Silicon Macs the effect is small (the system is already efficient at releasing memory itself), but it's safe and free. If you're comfortable with Terminal, you can skip the apps entirely.
For most non-technical users, a one-click menu-bar app is worth the $5.
Honest bottom line
If you want the simplest, cheapest legitimate option: Shiny. (I'd say that even if I didn't make it, because at $4.99 once for three Macs the price-to-job ratio is hard to argue with.)
If you want free with paid extras: Memory Cleaner.
If you like a visual graph: Memory Diag.
If you want a free toolkit and don't mind a dated UI: OnyX.
If you want a full Mac-maintenance suite and don't mind the subscription: CleanMyMac.
None of them are bad. They're tools for different jobs at different prices. Pick the one whose tradeoffs match what you actually need.