How to Boot from USB on Mac

Fancy testing the latest beta version of Mac? But are afraid to install it?

Like this, there can be several other reasons – troubleshooting Mac or installing a new update due to which you might want to boot Mac from USB. Here’s how to install macOS from USB and make macOS bootable USB.

What is a USB

USB or Universal Serial Bus, also known as a flash drive, is a portable storage device. Due to its portability, compatibility, affordability it is most commonly used across the globe to store any type of data.

This small device is used for several other purposes like storing, copying, transferring data and much more. In addition to this one most important thing, USB is used for is Booting Windows and Mac. But why do we need a bootable USB for Mac?

Reasons for Mac Boot from USB:

Booting/Installing macOS from USB gives users full control over macOS. This means if your Mac won’t start or is giving you any trouble you can get around to it by creating bootable USB for Mac. In addition to this, other common reasons why installing macOS from USB should be considered are:

  • It allows users to install a different version of macOS.
  • It gives users a chance to test the beta version before making the final decision.
  • Risk-free testing of the Beta version.
  • Faster and efficient.
  • Can install older versions to run your favorite apps that aren’t compatible with the latest macOS.

How to Boot from USB on Mac

Loading Mac from a bootable USB Mac is pretty simple. You just need to know the requirements and follow the steps explained below:


  • Intel-based Mac
  • USB thumb drive with GUID partition and OSX installer.
  • Minimum 12 GB of free space.

Note: Avoid booting earlier version of macOS X than the one your Mac was shipped with.

Now that you know what you need let’s get started.

Steps to boot Mac from USB

  • Attach USB to Mac machine.
  • Restart your Mac if already running or turn on your Mac.
  • When your Mac is about to start, press and hold the Option key to access built-in Startup Manager. Once the Startup Manager screen opens, free the Option key. The utility will now search for available drives including bootable.
  • Use arrow keys to select the USB drive you want to start Mac from.
  • Once done double click the selection. The machine will not start from the select bootable USB drive.

Using these simple steps you can Mac boot from USB. To learn in detail how to create bootable USB and boot Mac from USB read further.

How to Create a Bootable Installer for macOS

Step 1: Download macOS

Click the suitable download link to download macOS:

Step 2: Use the Terminal

Attach bootable USB Mac flash drive and open Terminal. You can find it under the Utilities folder of your Application folder.

Assuming the installer is still in the Application folder and MyVolume is the name of the USB you are using. Type in createinstallmedia and the following commands.

Catalina: *
sudo /Applications/Install\ macOS\ --volume /Volumes/MyVolume

Mojave: *

sudo /Applications/Install\ macOS\ --volume /Volumes/MyVolume

High Sierra: *

sudo /Applications/Install\ macOS\ High\ --volume /Volumes/MyVolume

How to Install macOS from USB

To boot Mac from USB you’ll need to select it during boot time. For this, you’ll need to use the Startup Manager feature. To use it follow the steps below:

Step 1: Restart or power on your Mac.

Step 2: Next, press and hold the Option key. This will open the Startup Manager and will list connected volumes and drives that can be used to boot macOS.

Step 3: Select the drive on which OS X is installed, you can use arrow keys to make the selection.

Step 4: Double-click to boot your Mac from the selected volume.

How to boot Mac from USB through System Preferences

Alternatively, you can use System Preferences to boot Mac from it. To do so follow the steps below:

Step 1: Open System Preferences > Startup Disk. You’ll see different various disk icons.

Step 2: Select the volume you’d like to use to start your Mac.

Step 3: Click the Restart button.

Your Mac will now boot using the selected device until you change it or override it from the Startup Manager.


If you run into problems while trying to boot your Mac from USB check this FAQ section:

What to do if Mac doesn’t boot from bootable USB drive?

If you face any problem while booting Mac from a USB drive or the drive with a bootable copy of OS X isn’t visible in Startup Manager, it might need repair.

To repair it head to Disk Utility to repair disk permission. If this doesn’t help you might have to reinstall OS X.

What type of USB can I use to boot Mac from USB?

Intel-based Macs support GUID partition type to boot Mac from USB

Why does my Mac shut down when I connect the USB drive?

If connected USB is damaged MacBook air automatically restarts as it contains a preventive measure that shuts it down when a USB storage device with the issue is connected.

This was all for now. Using this simple guide we hope you were able to load Mac using the bootable drive. This step will come handy when you want to troubleshoot any problem or want to load Mac from an external device.

We hope the steps were simple to follow. Do share your comments and let us know how you found the article. If you need us to cover any specific topic, please do let us know in the comments sections.

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