Mac running slow? What to check, in the order that helps
Mac running slow? Restart, then check Activity Monitor, free disk space, login items, browser tabs and updates. A plain checklist with real macOS paths.
If your Mac is running slow, restart it first, then open Activity Monitor and look for one app using a lot of CPU or memory. If neither explains it, make sure the startup disk has free space, switch off login items you don't need, close old browser tabs and install pending updates.
The order matters. The first two steps often sort out a slow Mac in a few minutes, and the later ones catch what is left. Further down are the system processes that look alarming but aren't, and the signs that it is the hardware rather than anything you can tidy.
Why is my Mac so slow? Restart it first
A Mac that has been running for weeks collects small problems: an app that slowly holds on to more memory, a background service that got stuck, an update waiting to finish. A restart clears all of them at once, which is why it is the first step and not the last.
- Save your work.
- Choose Apple menu > Restart.
- Untick Reopen windows when logging back in this time, so a misbehaving app starts fresh instead of returning in the same state.
If the Mac is fast again afterwards, you are done. If you want to know how long it had been running, here is how to check your Mac's uptime. And if it is slow again a day or two after every restart, something specific is building up, and Activity Monitor is the place to find it.
How do you find out what is slowing your Mac down?
Open Activity Monitor. It is in Applications > Utilities, or press Command and Space and type its name. Along the top are tabs for CPU, Memory, Energy, Disk and Network.
The CPU tab
Click the % CPU column header so the busiest processes come first. One app sitting near the top for minutes at a time, while you are not asking it to do anything heavy, is a strong suspect. To stop it, select it, click the stop button (an X in an octagon) in the toolbar, and choose Quit. Use Force Quit only if Quit does nothing.
The Memory tab
Along the bottom of this tab runs a Memory Pressure graph. Green means the Mac has enough memory for what you are doing. Yellow means it is working to keep up. Red, or yellow that never drops, means it is short. Next to the graph, Swap Used shows how much memory macOS has moved out to the startup disk. A few gigabytes of swap after a long day is normal. Lots of swap with the graph in red means you have more open than the Mac can comfortably hold, and quitting the biggest apps in the Memory column will help more than anything else in this post.
Processes that look scary but usually aren't
| What you see | What it usually is | What to do |
|---|---|---|
| kernel_task using a lot of CPU | macOS deliberately taking processor time to keep the Mac from getting too hot | Let the Mac cool: give it a hard surface, close heavy apps |
| mds_stores or mdworker busy | Spotlight indexing files, often after an update or a big copy | Leave it running; it settles down |
| photoanalysisd busy | Photos analyzing your library | Leave the Mac on and plugged in for a while |
| WindowServer high | The process that draws the screen; busier with many windows or displays | Close windows you don't need |
Don't quit processes you don't recognize, especially ones run by root or a system user. Many are part of macOS, and stopping them can make things worse.
Is your startup disk too full?
A Mac leans on free disk space constantly, and not only to store your files. Swap needs it, apps write temporary files to it, and updates need room to unpack. When the disk is close to full, everything slows down, sometimes badly.
Check in System Settings > General > Storage. If the free space at the end of the bar is a sliver, clearing room is likely to do more for speed than any other step here. The usual culprits are the Downloads folder, old installers, device backups and large videos, and what to clear when the startup disk is almost full goes through them one by one.
Cut down what runs all the time
Some slowness is not one heavy app but many light ones that never stop.
Login items and background items
Open System Settings > General > Login Items & Extensions (named Login Items before macOS Sequoia). The Open at Login list shows apps that launch every time you log in. Remove the ones you don't need straight away with the minus button.
Below it, Allow in the Background lists helpers that apps run even when the app itself is closed: update checkers, sync tools, menu bar utilities. Switch off anything you no longer use. You can turn an item back on any time, though the app it belongs to may stop doing some tasks while it is off.
Browser tabs and extensions
Each browser tab can be its own process with its own memory. Forty tabs left open for a week can weigh more than everything else on the Mac. Close what you have finished with, and bookmark what you are keeping "for later".
Extensions run on every page you open. If the browser is the slow part, try a private window, where most extensions are off by default, or switch extensions off one at a time in the browser's settings. In Safari they are in Safari > Settings > Extensions.
Why is your Mac slow after an update?
For a while after a macOS update, or after moving to a new Mac, macOS rebuilds its Spotlight index and Photos may re-analyze your library. Both use processor time and can make the Mac feel sluggish for a day or so. Leave it on, plugged in and awake for a few hours and it usually catches up.
The opposite is also true: skipping updates can leave you with a known bug that slows things down. Check System Settings > General > Software Update for macOS, and the App Store's Updates page for apps from there. If one particular app is the slow one, update it before anything else. Whether to take a big new version of macOS straight away is a separate question, covered in whether to install macOS updates right away.
When the slowness is the hardware
If the Mac is still slow after all of that, two built-in tests help you tell software from hardware.
Safe Mode starts the Mac with only what it needs, skipping login items and some extensions, and checks the startup disk. On a Mac with Apple silicon, shut down, then hold the power button in until the screen says "Loading startup options". Select your startup disk, hold Shift and click Continue in Safe Mode. On an Intel-based Mac, restart and hold Shift until the login window appears. If the Mac is clearly faster in Safe Mode, something that loads at startup is the cause, so go back to login items. Restart normally to leave Safe Mode.
Apple Diagnostics checks the hardware. On Apple silicon, hold the power button as the Mac starts until you see the startup options, then press Command and D. On an Intel-based Mac, hold D while it starts up. It gives a reference code if it finds a problem.
Some limits are just the machine. An older Mac with little memory will struggle with today's browsers and video calls however tidy it is, and older iMacs with a spinning hard drive are slow at almost everything. If the hardware tests come back clean and the Mac is still slow, back it up and contact Apple Support. Reinstalling macOS from Recovery, which keeps your files, is an option they may suggest, but only with a recent backup in hand.
Keep it from slowing down again
Most of the habits that keep a Mac quick are boring: restart about once a week, keep some free space on the disk, quit apps you are done with instead of hiding them. The hard part is remembering, because a Mac that sleeps every night can go weeks without a restart unless an update forces one.
Notchpals can do the remembering for two of them. Among the characters it keeps in your notch are Tech care ones, and they watch uptime and free space. They don't speed anything up or look at your CPU. If Otto, the octopus juggling more than he can hold, is in your crew, he shows up during working hours when a restart is overdue, and never more than once a week.
OttoOver a week without a restart! Too many things open. I know the feeling.
He also turns up when the startup disk drops below 10 percent free, again at most weekly, which is usually well before the disk is full enough to drag. Press Done once you have restarted or cleared some room.
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