Quick answer
A slow Mac is most often slowed down by apps that start automatically, a full disk, too many open tabs, and an outdated macOS. First open Activity Monitor and see what is using CPU and memory, then remove unnecessary login items and free up space. If it is still slow after that, check the temperature, battery, and disk health.
How to recognize the problem
- Apps take several seconds longer to open than before
- The fan is constantly loud and the case is hot
- The spinning beach ball appears when switching between windows
- The Mac takes a long time to wake from sleep
- Switching between tabs in the browser lags
Most common causes
Too many background programs
Apps that start automatically at login and run in the background use CPU and memory even when you are not using them.
Full disk
When there is little free space left on the disk, macOS has nowhere to write temporary files and the system slows down.
Outdated system or apps
Older versions of macOS and apps may have bugs that consume resources, and updates often fix them.
Browser with many tabs
Chrome and Safari with dozens of open tabs and extensions can use several gigabytes of memory on their own.
Overheating or weakened battery
When the Mac overheats, the processor automatically reduces speed, and a weakened battery on a MacBook can cause the same.
Step-by-step fix
- 1
Open Activity Monitor and find the culprit
Launch
Activity Monitorfrom the Applications > Utilities folder. Go to theCPUtab and click the% CPUcolumn header to sort descending. On theMemorytab, sort by theMemorycolumn. If an app you are not using is at the top of the list, first save your work, select it, and click the quit process button (X), then confirm. Do not quit processes that belong to the system or that you do not recognize. - 2
Remove unnecessary login items
Open
System Settings>General>Login Items(on older versionsSystem Preferences>Users & Groups>Login Items). In theOpen at Loginsection, remove anything you do not need immediately after startup, and in theAllow in the Backgroundsection, turn off programs you do not use daily. Do not touch items that clearly belong to system components. - 3
Close tabs and check browser extensions
In Chrome, open
chrome://extensionsand disable extensions you do not use, and in Safari,Safari>Settings...>Extensions. Close tabs you do not need and check if the speed has improved. The browser is often the biggest memory consumer on a Mac. - 4
Free up disk space
Open
System Settings>General>Storageand see how much space is free. If it is less than 10 percent of total capacity, first make a backup of important files, then delete large files from Downloads, empty the Trash, and remove old installer files. For more detailed cleaning steps, see the separate article on a full disk. - 5
Update macOS and apps
Open
System Settings>General>Software Updateand install available updates. Then in the App Store, open the updates tab and update the programs you installed from there. If an update gets stuck halfway, follow the separate article on that. - 6
Reduce visual effects
In
System Settings>Accessibility>Display, turn onReduce motionandReduce transparency. This will not speed up every Mac, but on older models it noticeably reduces graphics load and makes transitions smoother. - 7
Check temperature and battery
If the fan is constantly loud, check that the air vents on the case are clean and that the Mac is on a hard surface. On a MacBook, open
System Settings>Batteryand check the battery condition; if it says service is recommended, that could be the cause of the slowdown. - 8
Restart the Mac and check the disk
Restart the computer and see if the slowdown recurs immediately or only after a few hours. Then open
Disk Utilityfrom the Utilities folder, select the disk, and runFirst Aid. If you suspect a disk failure, make a backup first. This is a safe check that fixes minor errors in the disk structure.
If nothing helped
If the Mac is still slow after all the steps, check if the problem also occurs in a new user account. Open System Settings > Users & Groups, create a temporary account, and log in to it: if everything is fast there, the problem is in your data or programs in the main account. When the Mac is slow even during system startup, before doing anything that modifies the disk, make a backup using Time Machine or to an external disk. Only after that consider reinstalling macOS, which is a more demanding task and it is better to have someone with experience do it.
How to prevent it
- Keep at least 10 to 15 percent of disk space free
- Review items in `Login Items` every few months
- Install macOS updates regularly, do not postpone them for months
- Close tabs and programs you are not using while working
When to call a professional
If the Mac slows down even during startup, if Disk Utility reports errors, or if you suspect a disk or battery failure, it is better to leave the inspection to a service center or IT support than to change system settings yourself.
IT infrastructure maintenance · Servers, networks, backup, security and helpdeskFAQ
Is it normal for a Mac to use more than 80 percent CPU?
Short spikes are normal, for example during installation or video processing. If an app constantly keeps a high percentage even when you are not using it, check if it has an update or remove it from login items.
How much free space should I leave on the disk?
The rule is to leave at least 10 to 15 percent of total capacity. On a 256 GB disk, that means about 25 to 40 GB free, because macOS uses that space for temporary files and cache.
Will clearing the cache speed up the Mac?
Clearing the cache frees up space, but it is rarely the main cause of slow performance. First check Activity Monitor and login items, because that is where the real cause is most often hidden.