A USB 3 flash drive with fast read speeds would be a good choice.īe sure to quit (Command + Q) the macOS Catalina installer if it starts up after the download is completed.Ī copy of the macOS Catalina installer.This is usually downloaded via the Software Update preference pane (macOS Mojave and later), or the Mac App Store (macOS High Sierra and earlier). You should also consider using a fast flash drive.

Going larger isn’t a bad idea, though you can use the extra space on the flash drive to store apps and utilities you may need for troubleshooting purposes. Future versions may require larger flash drives, but for now, 8 GB is big enough. The list of items needed to complete this project is fairly basic, and I suspect you may already have everything you need.Ī connection to the Internet: You’ll need an Internet connection for downloading the installer from Apple.Ī USB flash drive: 8 GB is the minimum size required, at least for all the versions of the macOS through macOS Catalina. What You Need to Create a Bootable MacOS Installer It can be used as a bootable troubleshooting tool, letting you access the same apps that are found in the Recovery Volume.This bootable installer meets that requirement. This can usually be done provided you have a copy of the installer for the version of the Mac OS you wish to return to. You may have noticed that with each new version of the macOS that’s released, there are usually some users who have one or more issues with it and wish to return to a previous version. It allows you to archive a copy of the macOS installer, which you may need if you ever want to downgrade to the version on the installer.It lets you install the OS on multiple Macs without having to download the installer multiple times.By booting to the installer, you can perform a full erasure of your normal startup device before installing the new OS. It allows you to perform a clean install of the operating system on your Mac using the existing startup drive.There are multiple reasons for having a bootable macOS Catalina installer. Why Make a Bootable macOS Catalina Installer? Macs with Thunderbolt 3 can also use a USB flash drive as bootable media (an adapter may be required). All current Macs support booting from a USB port.You can buy a new USB flash drive large enough for this project for less than $10. It’s small and easy to store in a safe place.A bootable flash drive is the preferred method, however here’s why:

Create mac os x bootable usb