A quick word of context before we start. Your Mac has a fixed amount of memory (RAM) to run apps. When that memory fills up completely and macOS can't free any more, it shows you this dialog. It is not a hardware fault and it is not permanent. It means the system hit a ceiling and needs you to clear some space.
The fix is straightforward. The steps below go from "do this right now" through to longer-term prevention.
What to do RIGHT NOW when you see the error
The dialog box macOS shows you is not just a warning, it is also a tool. It lists the apps it recommends closing, and it has a Force Quit button.
Here's the order of operations:
- Save anything you can. Click into any app that is still responding and save your work (Command-S). Even a few seconds of saving is worth it. Apps like Pages and Word have autosave, so those are probably fine. A custom spreadsheet you have been editing since this morning might not be.
- Click Force Quit on the apps macOS suggests. The dialog shows which apps are consuming the most memory. Trust it. Force quitting them releases their memory immediately and usually lets the rest of your system recover.
- Wait 30 seconds. After force quitting, macOS reclaims and redistributes the freed memory. Give it a moment before you conclude things are still broken.
In most cases, that is enough. Your Mac stabilises, you reopen what you need, and you move on.
If your Mac is completely frozen
Sometimes the dialog itself won't respond to clicks. The whole screen is stuck. At that point, there is one option: a hard shutdown.
Hold the power button for about 10 seconds until the screen goes black and the Mac turns off. Then press the power button once to start it back up normally.
This is safe for your hardware. It is not a gentle shutdown, so you will likely lose unsaved work in any app that was open. But if the system is already unresponsive, that work may already be gone. A hard shutdown stops the spiral and gets you back to a working state.
After it reboots, do not immediately reopen every app that was running. Open only what you need right now.
After the immediate fix: identify the cause
Once you are back to a working Mac, take five minutes to find out what caused it. macOS ships a free tool that shows you exactly what is using memory. It is called Activity Monitor.
How to open it:
- Press Command-Space to open Spotlight.
- Type "Activity Monitor" and press Return.
- Click the Memory tab at the top of the window.
- Click the Memory column header to sort the list biggest first.
Whatever is at the top is the culprit. For most people it is one of these:
- Google Chrome with a lot of tabs open (often 2 to 4 GB on its own)
- Slack after a long session without quitting (often 1 to 2 GB)
- Photoshop or Lightroom left open from earlier in the day
- Final Cut Pro or Premiere with a large project loaded
If you want to close an app from here without switching to it, click it once to select it, then click the small stop-sign button in the toolbar (top-left of the Activity Monitor window) and choose Force Quit.
Avoid force-quitting anything labelled "kernel_task", "WindowServer", or "loginwindow". Those are macOS itself and should be left alone.
While you are here, glance at the Memory Pressure graph at the bottom of the window. See what memory pressure means for a full explanation. Green is healthy. Yellow means working hard. Red means the system is struggling. If you just recovered from the error, it should now be green or yellow. If it is still red, close more apps. For a deeper walkthrough of Activity Monitor's memory tools, see how to use Activity Monitor on Mac.
Long-term prevention
If this has happened once, it can happen again. The good news is that a few small habits cut the risk dramatically.
Quit apps you are not using. This is the single biggest one. Closing a window is not the same as quitting the app: the app stays loaded in memory in case you come back to it. To actually quit, right-click the icon in your Dock and choose Quit, or press Command-Q when the app is active. Read more about this in how to free up RAM on Mac.
Restart at least once a week. Over a week of continuous use, macOS accumulates fragments of memory from apps you opened and closed. A restart wipes all of that. Apple menu, Restart. It takes two minutes and makes a noticeable difference if you rarely restart.
Reduce Chrome tab count. Each Chrome tab is a separate process with its own memory footprint. Twenty tabs can easily consume 3 to 4 GB. Close tabs you are not actively using, or use a tab manager extension to suspend idle ones.
Watch memory pressure, not just memory used. macOS deliberately fills memory to make things faster. High memory use is not automatically a problem. What matters is whether the Memory Pressure graph in Activity Monitor is red. If it is persistently yellow or spikes to red under normal use, that is a warning sign worth acting on.
When is it just time for more RAM?
Sometimes the honest answer is that 8 GB is not enough for how you use your Mac. If all of the following are true, it may be time to look at an upgrade:
- You see the error regularly, even after quitting Chrome and other heavy apps.
- Memory Pressure stays yellow or red even when you only have a few apps open.
- You work with video, photography, or audio in professional tools.
- Your Mac is under four years old, so an upgrade is a real option rather than a repair.
Apple's own guidance on how to check if your Mac needs more RAM is a good starting point. The short version: if Memory Pressure is frequently yellow or red and you have already quit everything you reasonably can, more RAM is the right fix.
For most people, though, the error is caused by habit rather than hardware. A few open apps too many, a browser left running since Tuesday, a restart that has not happened in two weeks. Fix those first.
A tool that handles this automatically
Stopping memory pressure before it gets to red is what Shiny does, in one menu-bar click. It sits quietly in your menu bar and watches the memory pressure graph. When pressure climbs, one click asks macOS to release inactive memory, closes orphaned helper processes, and pauses apps that have been idle for hours but are still holding RAM. The kinds of things that, done manually, add up to the steps above. $4.99 once, no subscription.
Disclosure: I make Shiny, so I am biased. The manual steps in this post are free and work just fine. If you find yourself hitting this error more than once a month, a $4.99 one-click button might save you more than it costs.