How to create a bootable USB drive on Mac

6 min read

There are times when having a bootable USB drive with macOS installation files can be a life-saver. Not only will it help you reinstall macOS and fix your Mac in case it won’t turn on, you can also use the drive to install new macOS on as many Macs as you like. 

There is even an argument to be made about having an Apple backup and fresh macOS installer on a bootable drive available at all times. Here, we’ll walk you through why you may want to do so.

What is a bootable USB or external drive?

Simply stated, a bootable USB Mac drive is one that has a version (or versions) of macOS available on a disk that isn’t your machine. Whether it’s an external hard drive or a USB ‘thumb’ drive, both are considered bootable drives. 

For the sake of clarity, we’ll simply refer to any external drive as a USB drive.

What you need to create a bootable USB for Mac

Before we begin, here are two main things you need to create a bootable USB: 

  • An external drive (USB flash drive or any other type) with at least 14GB of free space. The drive should be formatted as Mac OS Extended. 
  • macOS installer files. We’ll explain how to get those files on your Mac in a sec. 

How to get macOS installer files 

 Do you have your external drive ready? Great! Let’s grab the installer files now. At this point, you should be very careful because 1) there are different ways to download installer files, depending on the macOS version, so you should choose the right download method; 2) you should download installer files but shouldn’t install new macOS on your Mac — when the installation starts, make sure to terminate it right away. 

Installers for newer versions (from High Sierra to Monterey) can be downloaded from the App Store as applications and saved to your Applications folder. Before you go to the App Store, check if your Mac is compatible with the macOS you’re going to download and make sure your Mac is currently running macOS Sierra 10.12.5 or later. 

If you’re good to go, grab the installer file:

macos installer file

If you want to download an older version installer — OS X El Capitan — note that it will be downloaded as a disk image to your Downloads folder. Importantly, you should download the DMG file through Safari. From the DMG, install an OS X El Capitan app — this is the app you can create your bootable installer from. 

How to make bootable USB on Mac

Once you have your macOS installer files, you can move on to creating a bootable USB. Prepare your formatted drive and let’s dive into it. There are two ways to solve the task: the quick one — using Disk Drill, and a bit more laborious — using Terminal. 

How to create a bootable installer for macOS with one click 

Connect your external USB to Mac and open Disk Drill (it’s available with Setapp): 

  1. In Disk Drill, choose ‘macOS Installer’ in the sidebar 
  2. Check a quick how-to video or get right to it 
  3. Choose macOS installer or upload it manually
  4. Choose destination (your external drive) 
  5. Create macOS installer. 

create a bootable installer macos

 We love this method because you literally can’t go wrong here — there’s no chance you’ll make any error in a Terminal command because you don’t have to deal with commands. What’s more, Disk Drill can be used for data backup, file recovery, disk cloning, and more.

Make bootable USB on Mac using Terminal 

 If you don’t have Disk Drill, try the Terminal method to create a bootable external drive for Mac: 

  1. Connect the USB drive to your Mac
  2. Open Terminal 
  3. Depending on the version of macOS you downloaded, enter one of the following commands:
  • Monterey: sudo /Applications/Install\ macOS\ --volume /Volumes/MyVolume
  • Big Sur: sudo /Applications/Install\ macOS\ Big\ --volume /Volumes/MyVolume
  • 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
  • Sierra: sudo /Applications/Install\ macOS\ --volume /Volumes/MyVolume --applicationpath /Applications/Install\ macOS\
  • El Capitan: sudo /Applications/Install\ OS\ X\ El\ --volume /Volumes/MyVolume --applicationpath /Applications/Install\ OS\ X\ El\

Note: If your USB drive has a unique name, replace ‘MyVolume’ in the command with the name of your USB drive. If you read the command, you’ll see your Mac is taking the version of macOS you downloaded from your Applications folder and placing it on your USB drive.

After entering the command, do the following:

  • Press ‘Return’ or ‘Enter’ on your keyboard
  • When prompted in Terminal, enter your administrator’s password
  • Press ‘Return’ or ‘Enter’ on your keyboard
  • When prompted in Terminal, type ‘y’ to confirm you’d like to erase the USB drive.

When finished, Terminal will show the volume has the same name as the installer you downloaded. You can now quit Terminal and eject your USB Drive.

How to boot your Mac from a USB drive

Now that you’ve created a bootable installer for your Mac, you can use it to boot Mac using a fresh install of macOS. Once again, let us warn you that you should only install macOS on a supported device. There are some workarounds for installing macOS on unsupported devices but they require serious technical expertise and we don’t recommend trying them out unless you’re a power user. 

Here’s how to boot from USB on M1 Macs: 

  1. Plug the bootable USB drive into a compatible Mac
  2. Turn on Mac while holding the power button
  3. Once you see the startup options screen, select the drive with a bootable installer and click Continue
  4. Follow the prompts. 

Here’s how to boot from USB on Intel Macs:  

  1. Plug the bootable USB drive into a compatible Mac
  2. Press and hold Option right after turning on your Mac
  3. Release Option once you see the startup options screen
  4. Select the drive with a bootable installer and press Return
  5. In the Utilities window, choose ‘Install macOS’ and click Continue
  6. Follow the prompts. 

Don’t forget to back up your files

And the most important step you should never miss — please back up your essential files before booting from a USB. You can do this manually by digging through your files and loading them onto a separate USB drive, but there’s a better way.

backup files disk drill

Another backup tool that is also available with Setapp is called Get Backup Pro. It’s a lot like Apple’s Time Machine but allows for much better control. For example, you can select the files you want to back up, without wasting storage to back up redundant stuff.  

backup get backup pro

Get Backup Pro also compresses your backups, allows for scheduling of automatic backups, and allows you to recover from an external drive onto any computer — which is something that Time Machine can’t do. 

If you want to free up storage before installing a fresh copy of macOS, CleanMyMacX will be of great help. It removes all redundant files and system clutter from your Mac in one scan. We highly suggest running this prior to any installation of macOS from a bootable USB drive.

Clean up storage

Keep Setapp at hand when installing new macOS

Having a USB drive with a ‘clean’ version of macOS is always a good idea. When things go amiss, it’s nice to have an easy way to start from scratch. 

But this doesn’t transfer files, which is why we suggest using Disk Drill and/or Get Backup Pro to create a backup in advance. Utilizing one (or both) will help your files stay somewhere safe, so you never have to worry. We also advocate for using CleanMyMacX before any backup, which helps ensure your system – and backups – are optimized. All three are available as part of a free seven-day trial of Setapp, along with dozens of other great apps for Mac. 

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