Starting up in “safe mode” may help you diagnose problems you’re having with your Mac. In safe mode, the operating system does not load any application or process other than the base system functions.
Safe Mode is a way to start up your Mac that performs certain checks and prevents certain software from automatically loading or opening.
Starting up in Safe Mode does several things:
- It forces a check of the startup volume, just like the First Aid feature of Disk Utility. You may see a progress bar on the screen during this check, and the computer takes longer than usual to complete its startup.
- It loads only required kernel extensions.
- It disables all fonts installed by the user.
- It moves font caches to the Trash that are stored in /Library/Caches/com.apple.ATS/(uid)/ – where (uid) is a user ID number such as 501 (Mac OS X v10.4 or later).
- It disables all startup items and login items in Mac OS X v10.4 or later.
- In Mac OS X v10.3.9 or earlier, Safe Mode opens only Apple-installed startup items (such items may be installed either in /Library/StartupItems or in /System/Library/StartupItems). These items are different from user-selected account login items.
Taken together, these changes can help resolve or isolate certain issues that exist on the startup volume.
Here’s how to do it.
1. Shut down your Mac and wait 10 seconds.
2. Press the power button.
3. Immediately after you hear the startup tone, hold down the Shift key.
You should press the Shift key as soon as possible after you hear the startup tone, but not before.
4. Release the Shift key when you see the gray Apple logo and progress indicator (spinning gear).
To leave safe mode, restart your Mac normally without holding down any keys during startup.
Safe mode will often allow you to delete or remove something that continues to restart every time you restart the computer. It also allows you to run diagnostics or look to see if an extension to the operating system could be causing your problem. It’s not something you do every day, but it certainly can be helpful.