Security Settings Do Not Allow This Mac to Use an External Startup Disk

What is “Security settings do not allow this Mac to use an external startup disk”

The “Security settings do not allow this Mac to use an external startup disk” error happens when you’re trying to select an external drive for booting, but macOS security settings are preventing it.

You’ll only see this error when you’re trying to boot from an external drive. If you’re trying to connect an external disk for another reason and can’t find it, check out our article on external hard drives not showing up on Mac.  

Why does error “Security Settings Do Not Allow This Mac to Use an External Startup Disk” occur

Apple has created a range of strong security features of macOS to keep your computer safe and protect your privacy. Of course, sometimes this can be frustrating–especially if you know you’re doing something safe.  

If you have a fairly new MacBook, iMac, or other Apple computer, it probably contains a T2 Security Chip or an Apple Silicon chip. These chips put some protections on your Mac to keep you safe–including preventing you from booting from external disks.  

By default, Apple’s Startup Security Utility is set up to allow your Mac to only boot up into a verified, legitimate operating system–rather than a potentially outdated boot disk.

In theory, this is a good idea–it means that you can’t accidentally boot up from a disk that contains malware or is corrupted, for example. However, if you know what you’re doing and you trust your external startup disk, you might need to access it and boot from it.  

Fortunately, you can change the default security and privacy settings to allow booting from external startup disks.

A note from our experts:

 

Sometimes your Mac settings don't allow you to use an external startup disk. Do you know how to fix this? Fortunately, our technical experts know and are ready to help you 24/7. MacKeeper's Premium Services feature will connect you with our consultants who can solve any Mac-related issue and teach you how to do it yourself.

 

How to access MacKeeper’s Premium Services:

1. Download MacKeeper and follow the on-screen instructions to install and activate it. Then open it.
2. Choose Premium Services from the sidebar.
3. Click Chat Now to start a secure conversation with a Mac expert.

How to fix “Security settings do not allow this Mac to use an external startup disk” issue

If you’re comfortable using Recovery Mode and changing some settings on your Mac, you can try to fix the issue yourself. However, I know that making changes to your MacBook can feel intimidating sometimes. So, if you’d rather talk to someone about the problem and get personalized help, you can use MacKeeper’s Premium Services.

The team at MacKeeper can help with all kinds of macOS issues, whether you’re having trouble with software, seeing unexpected error messages, or struggling with USB accessories disabled unexpectedly.

However, if you’re confident attempting to fix the “security settings do not allow this Mac to use an external startup disk” error yourself, I’ll explain how to do it.

Before we begin, you need to know whether your Mac has an Apple Silicon chip or an Intel Processor–this will change how you enter Recovery Mode.  

To find out whether your MacBook has an Apple silicon chip or an Intel Processor:

1. Go to Apple menu > About this Mac.
2. If it says Chip, you’re running an Apple Silicon chip, and if it says Processor, you’re running an Intel Processor.

Now you can enter Recovery Mode.

To enter Recovery Mode in a MacBook with an Apple Silicon chip:

1. Shut down your MacBook–you can do this by going to Apple menu > Shut Down.
2. When your Mac is completely turned off, press and hold the Power button until you see Options and your system volume.
3. Click Options and Continue.
4. Select your administrator account and press Next.
5. Enter your password when prompted, and choose Continue.
6. The Recovery app should now open.

To enter Recovery Mode in a MacBook with an Intel Processor:

1. Turn on or restart your Mac, and immediately press and hold Command+R.
2. If you see a lock symbol, enter your MacBook’s password.
3. Select your hard drive and then choose Next.
4. You may be asked for your administrator username and password–enter them if so.
5. The Recovery app should now open.

Important:

 

In Recovery Mode, you can fix a range of issues and change some preferences. For example, you might use Recovery Mode to repair disk permissions on Mac, reinstall macOS, or restore data from a Time Machine backup.

To fix the “Security settings do not allow this Mac to use an external startup disk” error:

1. Enter Recovery Mode.
2. When the macOS Utilities menu appears, go to Utilities > Startup Security Utility.
3. Enter your MacBook’s password and choose your admin account when prompted.
4. Enable Allow Booting from External or Removable Media.
5. Restart your Mac.

When your Mac restarts, you should be able to boot from an external disk.

Conclusion

When you’re trying to boot your Mac from an external startup disk, it can be frustrating to see an error message telling you that you can’t. However, macOS has disabled this as a security feature.  

Fortunately, you can easily change your security and booting preferences in Recovery Mode. If you need a little extra help, the team at MacKeeper’s Premium Services can help you find the solution.