An external drive that you can use as an installer for macOS Catalina is a handy thing to have. If you have multple Macs to upgrade, it’s a lot more efficient to plug in the USB installer drive and run the installer than to log into the App Store, download the 6.5GB OS installer, and then run it.
In this article I’ll go over the different ways you can create a bootable macOS Catalina installation drive. But before I give instructions on how to create the drive, I’ll go over the items you’ll need and how to get them.
Macworld also has bootable-install-drive instructions for:
Get an external drive and maybe an adapter
The macOS Catalina installer software is nearly 6.5GB, so you need a USB external drive that can hold that much data. The drive can be a thumb drive, hard drive, or SSD.
