Why is my Mac slow? How to find the cause

Is one app keeping the processor busy?

An app that’s exporting, rendering, syncing or stuck can take most of the processor, and everything else waits.

1. Open Activity Monitor. It’s in Applications > Utilities, or search for it with Spotlight.
2. Click CPU. Then click the % CPU column heading to sort the list, busiest first.
3. Look at the top of the list. Short spikes while apps open are normal. An app that stays at the top for minutes is the one slowing things down.
4. If you don’t need that app right now, quit it. Select it, click the Stop button at the top of the window, then choose Quit. Use Force Quit only for an app that isn’t responding, because unsaved work in it is lost.

Activity Monitor counts each processor core as 100%, so an app working on several cores can show more than 100%. This Mac has 15 cores, so Blender’s 978.6% means it’s keeping about 10 of them busy.

Is your Mac short of memory?

Look at memory pressure, not at how much memory is used. macOS works best when it uses all of its memory, including for files it may need again. Apple says unused memory doesn’t necessarily make a Mac faster.

1. In Activity Monitor, click Memory.
2. Read the Memory Pressure graph at the bottom of the window:
   • Green: your Mac is using its memory efficiently.
   • Yellow: your Mac might eventually need more memory.
   • Red: your Mac needs more memory.
3. If it’s yellow or red, click the Memory column heading to see which apps use the most. Save your work, then quit the ones you don’t need. Closing browser tabs you’re done with also helps.

If memory pressure stays yellow or red during your normal work, your Mac may need more memory. To see whether it can take more, hold Option, choose Apple menu > System Information, and click Memory. If you don’t see a Memory Slots section, its memory can’t be upgraded.

Is your startup disk nearly full?

Storage settings shows how full your startup disk is. Apple lists low free space among the things to check when a Mac runs slowly.

1. Choose Apple menu > System Settings, click General in the sidebar, then click Storage.
2. Try the recommendations at the top: Store in iCloud, Optimize Storage and Empty Trash automatically.
3. Click a category below them for more information and options.
4. Move large files you want to keep to an external drive, and delete files you no longer need.
5. Empty the Trash. Files in the Trash still take up space until you do.

If System Data looks large, What is System Data on a Mac? explains what it holds and what you can do about it.

Is your Mac too hot?

macOS doesn’t show a temperature, so go by touch and sound: the case feels hot, and the fans run fast. A Mac that gets very hot can slow down while it cools. Apple’s developer documentation says that at macOS’s two highest heat levels, performance may be affected, and at the highest level significantly.

1. Use your Mac on a stable surface with room for air. Soft surfaces such as beds and pillows block the air vents.
2. Keep the room between 10 °C and 35 °C (50 °F and 95 °F), and don’t leave a MacBook in a parked car.
3. Check Activity Monitor’s CPU list for an app working hard, as above. A busy processor makes heat.

What else can slow a Mac down?

• Apps that open at login. They open every time you log in. To see them, choose Apple menu > System Settings, click General, then click Login Items & Extensions. Select one you don’t need and click the Remove button (−).
• An app not made for your Mac. Apple suggests quitting any app that isn’t compatible with your Mac, for example one that needs a different processor or graphics card. System Settings > General > About shows your chip.
• A problem with the disk. Apple suggests using Disk Utility to check the disk and try to repair it.
• A macOS update that just finished. Spotlight indexes your files again after an update, which Apple says can take hours or even days. Mac slow after a macOS update? covers what’s normal.

Questions people also ask

Why is my Mac slow all of a sudden?

A sudden slowdown usually starts when something begins working in the background, such as an export, a sync or an update. Open Activity Monitor, click CPU and sort by % CPU to see what started. Why is my Mac suddenly slow? has more.

What does the spinning wheel on a Mac mean?

It’s the wait cursor: macOS shows it when an app is delayed by more than a few seconds. If it spins over one app, press Option-Command-Esc to force quit that app; if it spins in every app, the causes above are the usual ones. Spinning wheel on Mac? has the steps.

Is it safe to force quit an app?

Force Quit closes the app at once, so any work you haven’t saved in it is lost. Try Quit first, and use Force Quit only when the app stops responding.

Does high memory use mean my Mac needs more RAM?

No. macOS keeps memory busy on purpose. Memory pressure is what tells you: green is fine, and yellow or red during your normal work means your Mac is short of memory.