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

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While you can easily upgrade and install the latest macOS updates using the Software Update option on your Mac, there might be times when you need to do a clean installation of macOS for hardware/software troubleshooting or to install the same macOS on multiple devices. In that case, you'll have to install macOS from an external drive or USB.

Step 1: Download macOS

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

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

Each download of macOS is saved in the Applications folder as an app named Install macOS [version name]. If the installer opens automatically after finishing, quit it before proceeding. Make sure to download from a Mac using macOS Sierra 10.12.5 or later, or El Capitan 10.11.6, to get the correct installer. IT administrators should download from Apple, not from a local software update server.

Note: OS X El Capitan is different from the other five. This download comes as a disk image named InstallMacOSX.dmg.

Step 2: Create a bootable installer after downloading

First, you'll need a blank 16GB USB flash drive. If you're using an old USB drive to install, make sure you've copied off any data and backed it up, as the installation process will format and delete all data on the external USB to make it work. Additionally, the USB drive needs to be formatted as Mac OS Extended (HFS+).

• In the Finder, locate the Applications/Utilities folder, and double-click Terminal. • Each macOS installer requires its unique command line from the table below. It's recommended that you copy one of the commands below and paste it into Terminal. (You may need to replace every occurrence of MyVolume with the actual name of your USB flash drive.)

Monterey:

Big Sur:

Catalina:

Mojave:

High Sierra:

El Capitan:

When prompted, press Return to execute the command. You'll need to respond with a Y to all of the confirmation warnings that follow, including the one that confirms erasing the USB drive, allowing Terminal access to the files on the disk, and allowing the copy to proceed.

Step 3: Install macOS from the bootable installer

The steps to start up from a bootable USB drive differ for Intel-based Macs and Macs with Apple silicon.

Some basics about installing macOS from a bootable USB drive

Installing macOS this way can be challenging, as the process involves using terminal command lines and creating a bootable installer. However, we've aimed to make the steps straightforward and easy to follow so you won't get lost. Let's start with some common questions that many users have.

Q: Why am I installing macOS from USB?

Advantages of installing macOS from USB include:

• This is a good idea for a clean install, which will remove unnecessary apps and files that have built up on your Mac.
• It can help resolve startup issues with your Mac, fix corruption, or recover files.
• It saves time and effort when you need to install macOS on multiple systems or devices.

Question 2: How do I create a bootable macOS installer?

All the available installers can be found in the Mac App Store, including macOS Monterey, macOS Big Sur, macOS Catalina, macOS Mojave, macOS High Sierra, and OS X El Capitan. You'll need to use the correct terminal command for the different macOS versions to create the installer.

Question 3: Can I install macOS from a USB drive without an Internet connection?

The installer doesn't download macOS from the Internet, but it does require an Internet connection to obtain firmware and other information specific to your Mac model.

How to Retrieve Files After a Mac Factory Reset

Reinstalling macOS, Mac OS X, or performing a factory reset on your Mac is typically done when the system crashes, the computer runs slowly, or when a Mac user needs to wipe an old Mac for selling purposes...

To avoid the trouble of losing important data, it is recommended to back up your crucial files with Data Recovery Wizard for Mac before installing or updating macOS.

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Backup Your Mac and Never Lose Data

Back up and restore your MacBook/iMac without Time Machine, iCloud, or external hard drive.

Step 1. Click “Disk Backup” > “Create Backup” > “Next” on the main Disk Drill for Mac screen. You can create a drive backup image to protect your data from being overwritten.

Create disk backup with the tool

Step 2. Select the internal volume you want to back up, then click "Create Backup." If you're creating a backup and restoring data from an external hard drive, USB flash drive, or SD card, make sure to connect the storage device to your Mac beforehand.

Step 3. Choose a location to save the backup file, type a new name for it, and click Save. It is not advisable to save the backup on the same storage device from which you will be restoring your data.

[Additional Information] Create a macOS Bootable USB Drive on a Windows 11/10 PC

If you're on a Mac, the process is fairly straightforward. If you don't have access to a Mac, however, it's an entirely different story. Thankfully, there are some great Windows apps that can help you create a bootable macOS USB on your PC. One of the most popular is SysGeeker UltraDMG.

1. Download the macOS DMG image file, which is a bootable disk image containing the macOS operating system. You can find this online through a search.

Step 2: Click the link to download SysGeeker UltraDMG.

Step 3: When the process is complete, your USB drive will have the same name as the installer you downloaded (like Install macOS Monterey). Quit Terminal, then eject the USB drive. You should now be ready to proceed with the final installation steps.

Step 4: Load the macOS DMG file and click on “Burn” to create the bootable macOS installer! After about 10 minutes, you'll have a bootable macOS USB!

Conclusion

The three-step process, from downloading macOS to creating a bootable installer on an external USB and performing a clean install of macOS from it, should be straightforward. The procedure involves using Terminal command lines to erase the USB drive, format it with the appropriate file system, and save the installer on it. While unlikely, you can use a hard drive recovery software tool to retrieve files when reinstalling macOS.

Step 1: Launch Disk Drill for Mac when you're ready to recover data from the disk image. Select “Disk Images” in the sidebar and click “Recover” > “Next.”

Step 2: Navigate to the DMG file you created, and click "Open." If you saved the disk image to an external hard drive, plug in the backup drive to your iMac or MacBook.

Step 3: The tool will immediately start scanning, and you can filter lost files on the left pane. Select all the photos/documents/videos/email that you wish to recover and click on “Recover.” You can save the files locally/cloud or even restore them to iCloud by clicking on the “Save” button.