How to Install macOS from USB Bootable Installer in 3 Steps [Clean Install]

Follow the three steps to download the macOS bootable installer to an external USB and then install macOS from USB without a hitch. The process requires you to use the Terminal command lines and internet connection.

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You can easily upgrade and install the latest macOS update on your Mac machine using the system's Software Update option. That's no problem. But sometimes, we may require a clean installation of a macOS version for hardware/software troubleshooting or to be able to install the same macOS system on multiple devices at the same time. In this regard, you need to install macOS from an external drive or USB. 

Step 1. Download macOS

Click the download link for the MacOS version you want to install.

• macOS Monterey
• macOS Big Sur
• macOS Catalina
• macOS Mojave
• macOS High Sierra 

Each macOS download is going to be sent to the Applications folder as an app named Install macOS [version name]. If the installer opens after downloading, quit it without continuing installation. To get the correct installer, download it from a Mac that uses macOS Sierra 10.12.5 or later, or El Capitan 10.11.6. Enterprise administrators, please download from Apple, not a locally hosted software update server. 

Pay attention: OS X El Capitan is quite different from the other five. This download is presented in a disk image format named InstallMacOSX.dmg.

Step 2. Create the Bootable Installer After Download

First of all, a vacant 16GB USB drive is essential. If you want to use an old USB drive for installation, make sure that you've copied the data and saved it as a backup. The installer creation process will format and erase all data on the external USB to take effect. Also, the USB drive needs formatting as Mac OS Extended (HFS+).

Connect the external USB drive to your Mac. It'll be used for the bootable installer. Next, we'll arrive at the most important part of applying the 'createinstallmedia' command in Terminal to create the bootable installer for the following six operating systems.

• In the Finder, find the Applications/Utilities folder, then double-click Terminal.
• Each macOS installer needs an exclusive command line in the table. We suggest you copy one of the following commands and paste it in Terminal. (You may be required to replace MyVolume in all the command lines with the real name of your own USB flash drive.)

Monterey:

Big Sur:

Catalina:

Mojave:

High Sierra:

El Capitan:

After typing the command in Terminal, press Return to enter the command. Afterward, it's time to respond all the confirmation warnings by tying Y, including confirming erasing the USB volume, approving the Terminal to access files on the volume and allowing the copy to proceed.

Step 3. Install macOS from the Bootable Installer

To boot Mac from the bootable USB drive, the operation varies from the Intel-based Macs and Apple Silicon-based Macs. 

Some Basics of macOS install from a bootable USB Drive

Installing a Mac operating system in this way can be challenging, as the whole process involves the application of Terminal command lines and creating a bootable installer. Nonetheless, we're trying to make the entire procedure simple to follow and ensure you do not make mistakes. Now, let's begin with some of the most frequently asked questions that many users are trying to answer.

Q1: Why do you install macOS from USB?

The benefits of installing macOS from USB compared with the automatic software update option include:

• It's for a clean install, so you can get rid of junk apps and files that are piled up on your Mac.
• It's useful for troubleshooting Mac startup issues, fixing corruption, or recovering files.
• It can save time and effort when you need to install macOS on multiple systems and machines.

Q2: How do I create a bootable installer for macOS?

All the available installer can be found on the Mac App Store, including macOS Monterey, macOS Big Sur, macOS Catalina, macOS Mojave, or macOS High Sierra and OS X El Capitan. You need to create the installer using correct Terminal commands for different macOS versions. 

Q3: Can I install macOS from USB without the internet?

A bootable installer doesn't download macOS from the internet, but it does require an internet connection to get firmware and other information specific to the Mac model.

To prevent the inconvenience of losing important data, it is recommended that you back up your important files via the EaseUS Data Recovery Wizard for Mac before installing or updating macOS.

Step 1. Click "Disk Backup" > "Create Backup" > "Next" in EaseUS Data Recovery Wizard for Mac's main interface. You can create a drive backup image file in case the data is overwritten.

Step 2. Select an internal volume to back up, and click "Create Backup". If you want to create backups and recover data from an external hard drive, USB flash drive, or SD card, remember to connect the storage device to your Mac in advance.

Step 3. Choose a place to save your backup files, and change the name of your backup file, then click "Save". It is not wise to save backups in the same storage device that you want to recover data from.

[Bonus] Create a macOS Bootable USB on Windows 11/10 PC

The steps are quite simple if you were on a Mac. However, the situation is totally different if you don’t have a Mac at hand.  Fortunately, there are a couple of amazing Windows software out there that can help you create a macOS bootable USB on a PC. The most popular one is SysGeeker UltraDMG.

Step 1. Download a copy of macOS DMG file, a bootable disk image containing the macOS operating system. You can go and search from the Internet.

Step 2. Download SysGeeker UltraDMG by clicking the link.

Step 3. After all the operations are complete, the USB drive will have the same name as the installer you downloaded such as Install macOS Monterey. Quit Terminal and disconnect the USB drive. You should then move on to the final installation procedure now.

Step 4. Import the macOS DMG file and click the "Burn" button to make a bootable macOS installer! Wait about 10 minutes, and a bootable macOS USB will be ready for installation!

Closing Words

The three steps to download macOS, create a bootable installer to an external USB and then clean install macOS from USB should be clear and simple to follow. The process requires you to use the Terminal command lines to erase the USB drive, format it with a proper file system, and save the installer to it. Though the chance is little, use EaseUS hard drive recovery software to recover files while reinstalling macOS. 

Step 1. Launch EaseUS Data Recovery Wizard for Mac when you are ready to extract data from a disk image. Choose "Disk Backup" in the sidebar, and click "Recover" > "Next".

Step 2. Find the DMG file you have created before, and click "Open". If you save the disk image on an external hard drive, you need to connect the backup disk to your iMac/MacBook.

Step 3. EaseUS data recovery software will start scanning immediately and you can filter the lost files on the left side of the window. Choose all the photos/documents/videos/emails you want to recover, and click "Recover". You are allowed to save your files to local/cloud, and you even restore files to iCloud by clicking the "Save" button.