Create a bootable installer for macOS

You can use a USB flash drive or other secondary volume as a startup disk from which to install the Mac operating system. These steps are primarily for system administrators and other experienced users who are familiar with entering commands in Terminal.

• Why use a bootable installer?

• Download a full macOS installer from Apple

• Connect a USB flash drive to your Mac

• Use Terminal to create the bootable installer

• Use the bootable installer

Why use a bootable installer?

You don’t need a bootable installer to upgrade macOS or reinstall macOS. However, a bootable installer can be useful when those or other macOS installation methods are unsuccessful, or when you want to install macOS on multiple computers without downloading the installer each time.

Download a full macOS installer from Apple

To get a full macOS installer:

• Download macOS from the App Store or with your web browser using the download links and instructions in How to download and install macOS.

• Download from a Mac that is compatible with the macOS you're downloading. If downloading an older macOS, you may need to create the bootable installer on an older Mac that is compatible with it.

• Download from a Mac that is using the latest version of OS X El Capitan, or any later version of macOS. Find out which macOS your Mac is using.

• Enterprise administrators: download from Apple, not a locally hosted update server.

After downloading the installer:

• Make sure the installer is in the Applications folder of your startup disk. This is the folder that opens when you choose Go > Applications from the menu bar in the Finder. Move the installer into this folder, if necessary.

• Make sure the installer is named Install [Version Name], such as Install macOS Sequoia. It must be an installer app, not a disk image (.dmg) or package (.pkg) that contains the installer.

Connect a USB flash drive to your Mac

Connect a USB flash drive or other secondary volume to your Mac.

• When you create the bootable installer, this volume will automatically be erased.

• A 32 GB USB flash drive has more than enough storage space for any macOS installer, and 16 GB is enough for most earlier versions of macOS. If more space is needed, Terminal will let you know.

Use Terminal to create the bootable installer

1. Connect the USB flash drive directly to your Mac.

2. Open Terminal, which is in the Utilities folder of your Applications folder.

3. Depending on which macOS you downloaded, enter one of the following commands in Terminal. Each command assumes that the installer is in your Applications folder, and your USB flash drive is named MyVolume. If it has a different name, rename it or replace MyVolume in the command as needed.

   • Sequoia sudo /Applications/Install\ macOS\ Sequoia.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume

   • Sonoma sudo /Applications/Install\ macOS\ Sonoma.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume

   • Ventura sudo /Applications/Install\ macOS\ Ventura.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume

   • 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

4. When prompted, type your administrator password. Terminal doesn't show any characters as you type. Then press Return.

5. When prompted, type Y to confirm that you want to erase the volume, then press Return. Terminal displays the progress as the volume is being erased. If Terminal can’t erase successfully, use Disk Utility to erase the volume using Mac OS Extended (Journalled) format, then start again from the beginning.

6. If you see an alert stating that Terminal would like to access files on a removable volume, click OK to allow the copy to proceed.

7. When Terminal says that the install media is now available, the volume will have the same name as the installer, such as Install macOS Sequoia. You can now quit Terminal, eject the volume and disconnect the USB flash drive.

Use the bootable installer

Follow the appropriate steps based on whether the Mac on which you’re installing macOS is a Mac with Apple silicon.

Mac with Apple silicon

1. Before you begin:

   • This Mac must be compatible with the macOS that you’re installing. If it isn’t, it may start up to a circle with a line through it.

   • This Mac must be able connect to the Internet. A bootable installer doesn’t download macOS, but it does need an Internet connection to get firmware and other information for this Mac model.

2. Shut down or turn off the Mac.

3. Connect the bootable installer to the Mac.

4. Turn on the Mac and continue to hold the power button until you see the startup options window, which shows your bootable volumes, including the bootable installer.

5. Select the bootable installer, then click Continue.

6. When the macOS installer opens, follow the onscreen instructions.

Any other Mac

1. Before you begin:

   • This Mac must be compatible with the macOS that you’re installing. If it isn’t, it may start up to a circle with a line through it.

   • This Mac must be able to connect to the Internet. A bootable installer doesn’t download macOS, but it does need an Internet connection to get firmware and other information for this Mac model.

2. Shut down or turn off the Mac.

3. Connect the bootable installer to the Mac.

4. Turn on the Mac, then immediately press and hold the Option (Alt) key.

5. Release the Option key when you see a dark screen showing your bootable volumes, including the bootable installer.

6. Select the bootable installer. Then, click the onscreen arrow or press Return.

7. If you’re using a Mac with the Apple T2 Security Chip and you can’t start up from the bootable installer, make sure Startup Security Utility is set to allow booting from external or removable media.

8. Choose your language, if prompted.

9. Select Install macOS (or Install OS X) from the Utilities window, then click Continue and follow the onscreen instructions.

Find out more

If the Mac you’re using to create the bootable installer is using macOS Sierra or earlier, append --applicationpath to your command, followed by the appropriate installer path, similar to what is shown at the end of the command for El Capitan.