Safe Boot has been a staple of macOS ever since Jaguar OS X, providing Apple fans with an important way to troubleshoot problems with their Mac. But what exactly is Safe Boot? And how does it work?
What is Safe Boot, anyway?
Safe Boot is a way to startup your Mac with the minimum number of components required for it to run. Many components can become corrupt or damaged over time, so stripping your Mac’s startup process down to its bare essentials can help get your Mac up and running, even when it’s refusing to function in “normal” mode.
During Safe Boot, macOS performs a directory check of your startup drive and will attempt to repair any directory issues that it discovers. Your Mac will then disable all third party fonts and startup items, and will delete the dynamic loader cache on macOS 10.5.6 and higher. Finally, it’ll load the bare minimum kernel extensions it requires to run, and your Mac will then startup in Safe Boot mode.
Although Safe Boot is primarily used for troubleshooting and (hopefully) fixing a misbehaving Mac, the Safe Boot process also flushes many of the system cache files, such as font caches and kernel caches. This makes Safe Boot a quick and easy way to free up some space, without you having to track down every single system cache manually.
It’s worth noting that during Safe Boot you’ll be unable to use a number of features. Most notably, you won’t be able to play DVDs, capture video using iMovie, perform network file sharing (macOS 10.6 and higher), or listen to audio via external devices, such as headphones or speakers.
What’s the difference between Safe Boot and Safe Mode?
At this point, you may be wondering what’s the difference between Safe Boot and Safe Mode, especially since these terms are often used interchangeably.
Safe Boot is the process of forcing your Mac to boot using the minimum number of components, while Safe Mode is the mode that your Mac operates in once it completes a Safe Boot. Essentially, you Safe Boot into Safe Mode.
How do I Safe Boot?
If you’re encountering issues with your Mac, then it’s always worth checking whether your problems disappear in Safe Mode. Even if your Mac is refusing to boot normally, you may still be able to get it up and running, using Safe Boot.
If your Mac has a built-in or wired keyboard:
- Shut down your Mac, as normal.
- Press and hold the keyboard’s “Shift” key.
- Startup your Mac.
- Once your desktop or login window appears, release the “Shift” key. You should now be in Safe Mode.
If you’re using a Bluetooth keyboard, then the process is slightly different:
- Shut down your Mac.
- Startup your Mac.
- When you hear the distinctive Mac startup sound, press and hold the “Shift” key on your keyboard.
- Once your desktop or login window appears, release the “Shift” key. You should now be in Safe Mode.
If the issue(s) don’t reoccur in Safe Mode, then try restarting your Mac normally, as there’s a chance that the problems were related to a cache or directory issue, which Safe Boot has now fixed.
If the issue reappears as soon as you boot back into “normal” mode, then your problems may be linked to one or more apps that are set to launch automatically at login.
If you suspect this may be the case, then you should disable your login items, to see whether this resolves the problem:
- Select the “Apple” logo from your Mac’s menu bar.
- Navigate to “System Preferences… > Users & Groups.”
- In the left-hand menu, select your account.
- Click the little padlock icon in the bottom-left corner and enter your user password.
- Click “Unlock.”
- Select the “Login items” tab.
- Review the list of apps that are set to launch automatically every time you log into your user account. Select every application that you want to disable, and then click the little “-” icon.
- Restart your Mac, to see whether this has solved the problem.
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