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Create A Bootable USB macOS Installer for MacBook Air/Pro/iMac

Updated on Saturday, July 13, 2024

iBoysoft author Amanda Wong

Written by

Amanda Wong
Professional tech editor

Approved by

Jessica Shee


Summary: A detailed tutorial on how to create a bootable installer for macOS, including what you need to prepare, how to get the macOS installer, how to get the macOS installer onto your external storage, and how to use the bootable USB macOS installer.

How to create a bootable installer for macOS

Generally speaking, a bootable installer for macOS is an external storage media with a version of macOS installed. It is used to install an operating system on your Mac computer. Usually, Mac users straightforwardly upgrade macOS on their Macs. But sometimes, you may need a bootable installer for Mac. If so, this post is right for you on how to create a bootable installer for macOS. Or, you can use a Rufus for Mac tool to help you create a bootable USB drive for macOS.

When do you need a bootable macOS installer

Mac beats its competitors for delivering excellent performance and being user-friendly, but inevitably, a machine even your well-equipped Mac could go wrong from time to time such as MacBook won't turn on. When the MacBook Pro won't boot from internal hard drive, you can use a bootable macOS installer to boot Mac from USB to bring the Mac back on track.

In addition to using the bootable macOS installer to troubleshoot a malfunctioned Mac, creating a bootable installer for Mac also helps when you need to:

Essential preparations before creating a bootable installer

Before you proceed to the detailed steps for creating a bootable installer for macOS, you need to prepare the following things to guarantee the success of making a bootable macOS installer for your Mac, including:

  • A healthy Mac. You need a bootable Mac to create a bootable macOS installer.
  • A clean flash drive with 15GB at least. Theoretically, an external hard drive such as SSD and HDD can also be used as a bootable macOS installer, but a USB flash drive is always recommended given that it will be quicker compared with a standard hard drive. Besides, it should be 15GB or more. The size of the macOS installer has become larger and larger, the installer of Monterey is 12GB, and that of Big Sur is 13GB. You can back up the USB or transfer important files and then format USB on Mac to get a clean flash drive.
  • Identify the ports on your Mac. You should make sure the USB is compatible with your Mac's ports so that your Mac can successfully detect the USB flash drive. Using different USB ports also affects the speed. 
  • Choose a compatible macOS to install. You should identify your Mac model and check which macOS/OS X can your Mac run. Because you need to get a compatible macOS installer to create a bootable USB for Mac, only such a bootable macOS installer works for your Mac.

How to get the macOS installer

The first step to creating a bootable USB for Mac is to get the macOS installer of the version you prefer on a healthy Mac. You can get the latest macOS in System Preferences > Software Update and the Mac Apple Store, but you can't find macOS Mojave/Catalina/Big Sur in App Store or earlier versions of macOS there. 

The fact is that the installers of macOS High Sierra, Mojave, Catalina, and Big Sur are available in Mac Apple Store, but Apple hides them when you search for them in Mac Apple Store. You can use the links below to get the macOS installer in Mac Apple Store. For older installers like macOS Sierra, OS X EI Capitan, and OS X Yosemite on Apple's website. After downloading, the installer will open automatically, you should quit it to stop installing here. 

get macOS installer

How to make a bootable USB for Mac

Once the macOS installer has been downloaded on your Mac, you can make a bootable USB for your Mac now. Since the OS X Mavericks released in 2013, Apple has enabled Mac users to install macOS on an external storage media via Terminal commands. 

Be careful when you use the Terminal to create a bootable USB, and you can back up your Mac in advance to avoid data loss due to the mistaken operations. Now, follow the steps below to get the macOS onto your USB:

  1. Connect your USB drive to the right port on your Mac.
  2. Press the Command-Space key to open Spotlight, and search for Terminal.
  3. Launch the Terminal utility on your Mac.
  4. Type the correct command from the following, and replace "MyVolume" with the name of your USB drive.sudo /Applications/Install\ macOS\ Big\ Sur.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolumesudo /Applications/Install\ macOS\ Catalina.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolumesudo /Applications/Install\ macOS\ Mojave.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolumesudo /Applications/Install\ macOS\ High\ Sierra.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume
  5. Press the Return/Enter key to run the command. (Createinstallmedia: Command Not Found?)
  6. Enter your admin account password if asked and press Return/Enter.
  7. Type Y when it warns that the USB will be erased, then press Return/Enter.create bootable installer via Terminal
  8. It prompts "Copy complete and Done" when the process finishes.
  9. Eject the USB drive from your Mac.

Except for Terminal, you can also find an easier way to get the downloaded macOS installer onto your USB by using a third-party application. With the assistance of such an app, you are only a few clicks away from making a bootable macOS installer.

Now, you have successfully installed the macOS onto the USB flash drive to create a bootable installer for macOS. With it, you can proceed to troubleshoot an underperformed Mac with a startup issue, downgrade macOS on your Mac, batch upgrade macOS on multiple macOS, or install different macOS on Mac's second volume.

How to use the bootable USB on Mac

Before using the bootable USB on your Mac, you should change some settings of the Mac with a T2 security chip and Apple Silicon Mac so that you can boot the Mac from an external storage media. Thus, you need to access and change the settings of Startup Security Utility on your T2-secured or M1 Mac to allow your Mac to boot from USB.

change startup security settings on Mac

By the way, you can also set the Mac to boot from the USB once or every time by changing the startup disk on Mac, just select the bootable USB as the startup disk of your Mac. Then, you can boot Mac from USB and install macOS on your Mac. The specific steps vary from Apple Silicon Mac to Intel-based Mac.

The final words

Although you don't have to be tech-savvy to create a bootable installer for macOS, the steps are somewhat complicated to use the Terminal. You should carefully and patiently follow the guide to make a bootable macOS installer. You'd better always be prepared with an emergency bootable USB for Mac which can save the Mac once it undergoes serious issues.

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