How to Free Up Memory on Mac (macOS Sonoma, Sequoia & Earlier)

Your Mac is lagging. The fan is spinning like it's trying to take off. And then — the dialog nobody wants to see: "Your system has run out of application memory." OK. Take a breath. We'll fix this.

What follows is the order I actually try things, from 10 seconds of effort up to "fine, I'll restart." No Terminal required until step two, and even then only one command. On Apple Silicon (M1 through M4) memory pressure behaves a little differently than on Intel — I'll flag those moments as we go.

Quick answer: the 60-second fix

Open Activity Monitor → Memory tab.
Sort by Memory column (click the header).
Quit any app you're not using that's over 1 GB — especially Chrome, Slack, Teams, Electron apps, and anything listed as "Not Responding."
Close extra browser tabs. Each Chrome tab is often 100–400 MB.
Watch the "Memory Pressure" graph at the bottom. If it drops to green, you're done.

That's it for most cases. The rest of this guide is for when that isn't enough.

A quick detour: what "memory" even means on macOS

macOS doesn't treat RAM the way Windows does, and this trips people up constantly. "Free memory" will almost always be near zero on your Mac — that's not a bug. macOS uses spare RAM as cache, because empty RAM is wasted RAM. The number that actually tells you something is Memory Pressure, not Free.

Activity Monitor → Memory → the graph at the bottom:

Green — memory is fine, do nothing.
Yellow — macOS is actively compressing memory. Performance may dip.
Red — macOS is swapping to SSD. This is the slowdown you're feeling.

Your goal is to get out of red. Free memory is a lie; pressure is truth.

Step 1 — Kill the real culprits

In Activity Monitor, sort by Memory and look at what's on top. The usual suspects:

Google Chrome / Arc / Brave — each tab is a process. 30 tabs = 30 processes.
Slack, Teams, Discord, Notion — Electron apps. They eat RAM for fun.
Docker Desktop — default config gives itself 2–8 GB whether you're using containers or not.
Safari with YouTube or Google Docs pinned for a week straight.
Photoshop, Final Cut, Xcode Simulator, VS Code with big projects open.

Quit the ones you aren't actively using. Don't Force Quit unless the app is frozen — a normal quit is cleaner.

Step 2 — Purge inactive memory (the Terminal way)

macOS has a built-in command that asks the kernel to flush inactive pages. It's free, doesn't require any third-party app, and works on all recent macOS versions.

sudo purge

Type your admin password. The terminal will sit for a few seconds and then return. You'll often see Memory Pressure drop immediately, especially if you were hitting yellow.

Heads up

sudo purge is safe, but it's not magic. It discards disk caches macOS was holding onto for speed. Your Mac will feel slightly slower for the next minute while those caches rebuild, then normal again. Don't spam this command. Once is enough.

Step 3 — Restart background services that leak

A handful of system services just quietly get fatter the longer your Mac stays on: WindowServer, kernel_task, mds (Spotlight), cloudd (iCloud). Not exactly leaks in the textbook sense — more like slow weight gain.

The cheapest, unglamorous fix: restart the Mac. Really. If your uptime is north of a week and memory pressure is stuck in yellow or red, a reboot will do more than any cleaner on the App Store. Most of us haven't restarted in months because Apple made sleep too good to break the habit.

Step 4 — Use a Mac memory cleaner (when this actually helps)

Here's where cleaners earn their place. A memory cleaner does essentially what sudo purge does, but with two real improvements:

It does it on a schedule or on demand from a menu bar icon — no Terminal.
It can stop and restart specific processes that are leaking, without killing everything.

If you're an average user who doesn't want to open Terminal, that's a fair trade. MacFreeup's memory optimizer is the version we ship; OnyX has a similar tool in its Maintenance tab.

What a memory cleaner cannot do: add more RAM. If you've got an 8 GB M2 MacBook Air running Chrome + Slack + Docker, you're hitting a hardware limit no software can fix. The cleaner helps, but upgrading RAM on your next Mac is the real answer.

Step 5 — Reduce login items and background agents

Apps quietly install login items that run all the time — even when the app itself isn't open. Dropbox, OneDrive, Adobe Creative Cloud, Microsoft AutoUpdate, Zoom's ZoomDaemon, Spotify Helper, etc.

System Settings → General → Login Items & Extensions. Turn off anything you don't use. This alone can free 500 MB to 2 GB on a typical Mac.

Step 6 — Check for a misbehaving browser extension

One rogue Chrome extension can consume 2 GB on its own. If you're on Chrome and memory pressure stays red even after closing tabs:

Chrome menu → More Tools → Task Manager (Shift+Esc).
Sort by Memory.
Kill the extension or tab that's at the top.

Ad blockers with large filter lists and crypto-related extensions are the frequent offenders.

Step 7 — Free up disk space (yes, really)

macOS uses your SSD for swap when RAM is full. If your disk is over 90% full, swap has nowhere to go, and memory pressure stays high even when RAM itself isn't the bottleneck.

Free up 10–20 GB if you can. How to clean up a Mac covers the fastest ways to get there without paid tools.

How to prevent memory problems coming back

Restart your Mac once a week. It's the cheapest "optimizer" that exists.
Quit apps you aren't using instead of just closing the window. On Mac, closing the window ≠ quitting.
Cap Chrome tabs. If you need more than 20, use a tab manager like OneTab or Arc's tab archiving.
Turn off login items you don't use. Re-check this every few months.
If you're buying a new Mac: 16 GB minimum in 2026. 8 GB is not enough anymore, regardless of what Apple's marketing says.

FAQ

How do I free up application memory on my Mac?

"Application memory" in Activity Monitor means RAM used by currently running apps. To free it: quit apps you aren't using, close extra browser tabs, and run sudo purge in Terminal. If that isn't enough, restart the Mac.

What does "Your system has run out of application memory" mean?

It means macOS can't allocate more RAM for the app you just opened, even after compressing and swapping. Quit the largest app in Activity Monitor → Memory, then try again. If it keeps happening, you're chronically RAM-bound and should either reduce what you run simultaneously or upgrade.

Does rebooting actually free memory on Mac?

Yes — completely. A reboot clears RAM, swap files, and background services that may have leaked over days of uptime. It's blunt but effective.

Is there a free Mac memory cleaner I can actually trust?

OnyX and the free tier of MacFreeup both include memory cleanup without a paywall. The built-in sudo purge command is genuinely free but command-line only.

If you only remember one thing

The order that works for me, 9 times out of 10: quit heavy apps → close tabs → sudo purge or a memory cleaner → reboot if uptime is over a week → trim login items. The first three steps fix the vast majority of "my Mac is slow" complaints. Anything beyond that starts to be a hardware conversation — and on an 8GB Mac in 2026, sometimes that's just the honest answer.