Every computer may not boot up every once in a while, which can be irritating because it prevents you from getting into the system to view exactly what the problem is. The good news is there’s an easy(ish) workaround!


By booting from an external drive, like a USB for example, you can diagnose certain issues by accessing the internal drive with minimal effort.


That being said, many new Mac laptops don’t have USB-A ports, so it’s a good idea to obtain an external port that connects to a USB-C (USB Type C) port to really make the process easy-ish.


What is a bootable USB?


A bootable USB is a flash drive that allows you to both install an operating system (OS), and boot the computer from the external USB drive instead of the computer’s hard drive.


Whether a computer is brand new or becomes unusable from a compromised OS, you can use a bootable USB to install an operating system. You can run an OS installer like Windows, OSX, Mac, or specific versions of Linux from a bootable USB drive.


For Mac specifically, you can use a bootable USB to install MacOS Monterey, MacOS Big Sur, Catalina, Mojave, High Sierra, or El Capitan.


What you need to create a bootable USB for Mac


In order to create a bootable installer, there are three things you must possess:


1.A USB external drive that can plug into the Mac device you need it to, and contains at least 16GB of available storage, though in this case more is better.
2. A downloaded installation file for whichever MacOS (of the ones listed above) you’d like.
3. At least 36GB of available storage on the computer you wish to install the OS on.


It’s important to note that any and all existing data you have stored on the USB drive you plan to use will be deleted.


Depending on what version of macOS you want to install on the USB flash drive, you’ll need to download the installation files. You can obtain them from either the Software Update in System Preferences, or the Mac App Store.


That being said, the Mac App Store is probably going to be the less complicated option of the two.


How do I create a bootable USB drive for Mac?


Download the MacOS installer of the version you plan on installing on the USB flash drive. This should automatically download to your Applications folder as an app named Install macOS [version name].

  • Insert the USB drive to the computer.
  • Open Finder, and on the left click on the Applications folder. Scroll down to Utilities, click on it, then open “Disk Utility” and you should see your USB listed under “External” on the left side.
  • Click on your USB, then click on the “Erase” button at the top. It should bring up new fields for “Name,” “Format,” and “Scheme.”
  • Rename the drive to a title of your choosing, although we recommend a title that is suggestive of what is inside, something like “Booting MacOS.”
  • Select “Mac OS Extended (Journaled)” as the format.
  • Install the MacOS installer directly on the USB drive. You can do this by opening Terminal, which is located in the Utilities folder of the Applications folder.
  • Paste one of the commands listed below in Terminal. Please note that it assumes the installer is located in your Applications folder, and MyVolume is the name of the USB flash drive you’re
  • using. If it has a different name, replace MyVolume in the command with the correct name.


Monterey: sudo/Applications/Install\macOS\Monterey.app/Contents/Resources/createinstallmedia –volume/Volumes/MyVolume


Big Sur: sudo/Applications/Install\macOS\Big\Sur.app/Contents/Resources/createinstallmedia–volume/Volumes/MyVolume


Catalina: sudo/Applications/Install\macOS\Catalina.app/Contents/Resources/createinstallmedia –volume/Volumes/MyVolume


Mojave: sudo/Applications/Install\macOS\Mojave.app/Contents/Resources/createinstallmedia –volume/Volumes/MyVolume


High Sierra: sudo/Applications/Install\macOS\High\Sierra.app/Contents/Resources/createinstallmedia –volume/Volumes/MyVolume


El Capitan: sudo/Applications/Install\OS\X\El\Capitan.app/Contents/Resources/createinstallmedia –volume/Volumes/MyVolume –applicationpath /Applications/Install\ OS\ X\ El\Capitan.app


  • After typing the command, press Return.
  • You may see an alert that Terminal would like to access files, so make sure to click OK if this happens.
  • Once this stage is complete, the volume should have the same name as the installer you downloaded.
  • You can now quit Terminal and eject. Hurray, you did it!


Can you install Mac OS from USB?


Of course you can install a MacOS from a USB drive! Just follow the steps outlined below to find out exactly how to do so.


How to use the bootable USB for mac:


A bootable installer doesn’t download macOS from the internet, but oddly enough, it does actually require an internet connection, because it needs to obtain information specific to the Mac model.


Determine whether you’re using a Mac with an Intel processor, or with Apple silicon. Based on this information, follow the steps as instructed by Apple:


If your device is equipped with Apple silicon:


  • Plug the bootable USB into a Mac that is connected to the internet. Ensure that the device is compatible with the version of macOS you’re installing.
  • Turn on the computer and hold the power button until you see the startup options window.
  • Select the volume containing the bootable installer, then click Continue.
  • When the macOS installer opens, follow the instructions it will present to you.
  • If your device is equipped with an Intel processor:
  • Plug the bootable USB into a Mac that is connected to the internet. Ensure that the device is compatible with the version of macOS you’re installing.
  • Restart your computer, and then immediately press and hold the Option (Alt) ⌥ key.
  • Release the Option key when you see a dark screen showing your bootable volumes.
  • Select the volume containing the bootable installer, after which you should press Return.
  • Select Install macOS (or Install OS X) from the Utilities window, then click Continue and follow the instructions it will present to you.


You can expect the entire installation process to take at least 10 minutes, depending on the speed of your hardware.


Can I use Rufus to make a bootable USB for Mac?


Firstly, if you’re wondering what Rufus is, it’s a free and open-source app that helps format and create bootable USB flash drives. While making bootable USBs seems like it’s main purpose, Rufus can’t interpret the boot loader, and as such you can’t use Rufus to make a bootable USB compatible with Mac.


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