You’ll want a USB drive with at least 12GB of storage, but having more storage is never a bad thing. I recommend this SanDisk Ultra Dual Drive USB Type-C Flash Drive. It’s affordable, and comes with both a USB-C connection and a traditional USB-A connection. This is the drive that I’ve been using and my experience with it has been great.
Make sure that there’s nothing contained on the drive that you need, because this process will completely delete the contents of the drive.
Step 1: Download: macOS Big Sur, macOS Catalina, macOS Mojave, or macOS High Sierra
The will download to your 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 from a Mac that is using macOS Sierra 10.12.5 or later, or El Capitan 10.11.6. If required, click to download OS X El Capitan.
This downloads as a disk image named InstallMacOSX.dmg. On a Mac that is compatible with El Capitan, open the disk image and run the installer within, named InstallMacOSX.pkg. It installs an app named Install OS X El Capitan into your Applications folder. You will create the bootable installer from this app, not from the disk image or .pkg installer.
Step 2: Copy and paste text for the OS version that you want to create.
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
* If your Mac is using macOS Sierra or earlier, include the --applicationpath argument and installer path, similar to the way this is done in the command for El Capitan.
