How Do I Create a Bootable USB for Mac?

If you plan to install macOS on multiple Mac systems and don’t want to download the installer multiple times, then you can create a bootable installer.

You can use this bootable USB macOS installer to perform a clean install of macOS, install macOS from USB on a separate volume of your Mac drive, or in case your Mac encounters OS issues.

If you want to know how to create a bootable USB to install macOS Big Sur, Catalina, Mojave, and High Sierra, then this post is for you.

What’s Needed to Create Bootable USB for Mac?

Before you start, you need to keep the following things handy:

  • A USB thumb drive or any other external drive formatted as macOS Extended, with storage capacity of at least 14 GB.
  • A downloaded installer file of the macOS version, for which you have to create the bootable USB installer for Mac.
  • A good internet connection. 

Download macOS Installer File

To create bootable USB for Mac, you need to first download the macOS installer file. Follow the below steps to get the macOS installer file of Big Sur, Catalina, Mojave, and High Sierra:

  • Click on the macOS for which you want to download the installer file.
  • It will redirect you to the Apple website. A prompt appears asking you to use the App Store instead of the website. You can use the App Store to download the installer file.
Open App Store
  • In the App Store, you will find the macOS Installer, click on Get button on the top right corner.
macOS Installer
  • The installer file will start to download.
  • The above procedure will download the installer file in your Applications folder as an app named Install macOS Big Sur/ Catalina/ Mojave/ High Sierra. If the installer opens after download, close the prompt without continuing the installation.
Note: If you have macOS Catalina, then follow the steps below to download Big Sur installer:

System Preference > Software Update > Download macOS Big Sur.

Create Bootable USB for Mac

You can use the 'createinstallmedia' command to create bootable USB for Mac. Follow the steps below to create a bootable USB of any of the macOS mentioned above.

Note: The process described below applies to the macOS Maverick and later versions only.

Before you move ahead, here are a few facts that you must know:

  • Post Maverick, creating a bootable USB installer for macOS requires a single command (which we have given below for each macOS separately).
  • Insert the relevant command in the Terminal with utmost caution.
  • It is to be noted that the createinstallmedia command erases everything on your external USB drive. So, make sure you have nothing stored on the USB.

Step 1: Connect the USB thumb drive or any external volume to your Mac system.

Step 2: Launch Finder from Dock and open Disk Utility from the Applications section. Alternatively, press Command + Spacebar to open Spotlight search and type Disk Utility to find and open it.

Disk Utility Step 2

Note: If you are using High Sierra or later macOS versions other than Big Sur, click the View button on the top left corner and select the Show All Devices option from the dropdown menu.

Show all Devices

Step 3: Select the USB drive or external drive in the Sidebar (Select the root drive and not the volume).

Step 4: Select Erase. In the Erase prompt window, select Mac OS Extended (Journaled) as the format and GUID as the scheme.

Disk Utility Select Erase Option">
Note: Your drive might be shown as Untitled by default, rename it if you want.

Step 5: Again click Erase and wait till Disk Utility creates the partition and prepares your USB drive. Click Done.

Click on Done Button

Step 6: Launch Terminal from Utilities folder in Applications or simply search it using Spotlight (Command + Spacebar).

Utilities Terminal ">

Step 7: Copy the createinstallmedia command (from the section below) for the respective macOS you wish to use.

Step 8: Replace MyVolume with the name of your drive and hit Return.

Step 9: Terminal will ask for the Admin password. Type the Admin Password of your Mac and press Return.

Type the Admin Password of your Mac and press Return

Step 10: ‘To continue we need to erase the volume at /Volume/Untitled’ message will appear in the Terminal. Press Y and hit Return. You will find Erasing 0% … 10% … 20% appearing in the Terminal. Wait till it shows 100%.

Erase the volume at /Volume/Untitled
Caution: The process will erase everything from your USB drive or external hard drive. If you accidentally deleted some important data, you can use Stellar Data Recovery Professional for Mac to recover data from your internal and external hard drive or USB thumb drive.

Step 11: Once erasing is complete, the Terminal starts copying the macOS installer file on your USB drive.

Step 12: When the copying process completes, Copy Complete message appears on the Terminal panel.

Close the terminal. The bootable USB Installer drive for Mac is created. Now, you are all set to install the macOS on any Mac. 

The createinstallmedia Commands for different macOS

Note: In the given commands, replace ‘MyVolume’ with your drive’s name.

Big Sur

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


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


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

High Sierra

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

How to use the bootable USB drive for Mac?

It would be best to determine whether you are using an M1 Mac or Intel chip-powered Mac.

Make sure that your Mac has a good internet connection and is compatible with the macOS version you are about to install.

Then, follow the below instructions:

For M1 Mac or Apple Silicon

  • Plugin the bootable USB installer drive into your Mac system.
  • Switch on your Mac and hold the power button till the Startup Options window appears, showing bootable volumes.
  • Select the bootable USB drive and click Continue.
  • Follow the instructions on the screen in the macOS installer window.

For Intel Chip Powered Mac

  • Plugin the bootable USB drive in your Mac system.
  • Press and hold the Option key (⌥) immediately, once you have turned on or restarted your Mac.
  • Release the Option key once a dark screen showing bootable volumes appears.

Note: Before you proceed, make sure that the External Boot setting in Startup Security Utility is selected to allow booting from external media.

  • Choose the volume you created as bootable USB installer drive and click Return.
  • From the Utilities window, choose Install macOS or OS X.
  • Click Continue and follow the instructions that appear on your Mac’s screen.


A bootable USB drive is helpful when you want to download macOS on multiple systems or on a different volume of the hard drive. For this, you need a USB drive, with at least free storage space of 14 GB.

However, if there’s some data in the USB drive, it gets deleted or erased by the Terminal command. You can recover deleted/lost data on your device and any external drive by using Stellar Data Recovery Professional for Mac.

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To create a bootable USB for Mac, it should be Mac OS Extended (Journaled) format. You can change the format of your USB using the Disk Utility app on Mac. This format on USB will allow Mac to read and write files.
To make a USB compatible with both Mac and Windows, you need to format it using Disk Utility on Mac and then change the file format to ‘MS-DOS(FAT)’ in the Format menu of Disk Utility. This will make the USB readable and writable on Mac and Windows. However, this format of a USB drive would not allow you to create a bootable USB for Mac as it requires Mac OS Extended (Journaled) format.
No, Rufus supports only the Windows OS currently. However, if your Mac has Windows as a dual boot option, you can run Rufus on it. Rufus only supports 32-bit and 64-bit versions of Microsoft Windows.
About The Author
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Ashutosh Kumar

Tech Enthusiast and Senior Writer at Stellar®

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