Why is my Mac so slow? Check the disk first
Why is my Mac so slow? Most often the answer is the disk. When the startup disk is nearly full, macOS has no room for the swap files, caches and updates it relies on, and everything slows down, startup included. Less often it is too many apps opening at login, one busy app or too little memory. Here is what to check, starting with the most likely cause.
- Open MacWashing and choose System Junk in the sidebar.
- Click Start Scan.
- Look through what it found and click Clean. Anything debatable stays unchecked.
Free trial · macOS 14 or later
Is the disk nearly full? The most likely cause
macOS uses free space on the startup disk as an extension of memory, for caches and for updates. When it runs low, apps open slowly and the whole Mac feels sluggish. Apple lists it first among the reasons a Mac runs slowly.
- Choose Apple menu › System Settings.
- Click General in the sidebar, then Storage. The bar at the top shows how much space is used and how much is left.
- Click the ⓘ button next to Documents to see the largest files and delete the ones you no longer need.
If the bar is almost full and only a few gigabytes are left, this is very likely why the Mac is slow. See how to free up space on Mac. If there is plenty of free space, deleting files won’t make it faster: check the next sections.
Why is my Mac slow to start up?
A Mac that takes long to start up usually has a nearly full disk or too many apps that open at login. Each of them starts every time you log in and keeps running in the background.
- In System Settings › General, click Login Items & Extensions (in macOS Sonoma, Login Items).
- In the Open at Login list, select an app you don’t need right after startup and click the Remove button (–) below the list.
To find a login item that causes trouble, Apple suggests removing them all, restarting, then adding them back one at a time. More in how to stop apps opening at startup. If startup stays slow even without login items, start the Mac once in safe mode: it loads only what macOS needs, so you can see whether software that starts with the Mac is to blame.
Is one app or the memory to blame?
- Open Activity Monitor: Applications › Utilities › Activity Monitor.
- Click Memory and look at the Memory Pressure graph at the bottom. Yellow or red means the open apps need more memory than the Mac has: quit the ones you aren’t using.
- Click CPU and sort the list by % CPU. An app that stays at the top while you do nothing slows everything else down.
What to do next is in how to speed up a slow Mac.
Check the disk for errors
Apple also names disk problems among the causes. Disk Utility checks the disk and fixes what it can.
- Open Disk Utility in Applications › Utilities, select the startup disk in the sidebar, click First Aid, then Run.
With MacWashing, it’s one click
When the disk is nearly full, System Junk in MacWashing frees space quickly: it finds app caches, logs, old installers and leftovers of deleted apps and clears them in one go. It won’t make a Mac with plenty of free space any faster.
Free trial · macOS 14 or later
Questions and answers
Will MacWashing delete my own files when it cleans?
No. It removes only what it can match to a known app or a known kind of junk, in places apps leave files; macOS and Apple’s files are never touched. Anything debatable is marked and stays unchecked until you decide.
What about apps that are open?
If an open app holds files being cleaned, MacWashing waits for it to quit or quits it at your request, and opens it again afterwards.
Is it free?
Yes, within the free trial: System Junk and the Uninstaller free up to 25 GB in total, with no account or card needed.
Why is my Mac so slow all of a sudden?
Usually something has changed: the disk filled up with a large download or backup, a new app started opening at login, or an app got stuck using the processor. Check free space first, then Activity Monitor.
How much free space does a Mac need to run well?
Apple gives no exact figure. The fuller the disk, the less room macOS has for swap files, caches and updates, so keep a comfortable margin, especially before a macOS update.
Will cleaning my Mac make it faster?
Yes, if the disk was nearly full: freeing space gives macOS room to work again. If there was plenty of free space, deleting files won’t change the speed. Then look at login items, memory and busy apps.