This guide will show you how to make an install drive from either the Developer or the Public Beta version of the macOS Catalina 10.15 application. Having an install drive allows for deployment to multiple computers without re-downloading, performing clean installs, and booting to the installer’s in-built recovery tools for troubleshooting.

Once Catalina is out of beta, I’ll update the guide with the instructions for the general release.

To get started you’ll need the Install macOS Catalina Beta application and an external storage drive larger than 8GB. A USB thumb drive is usually best for this, but you could also use an SD card or an external hard drive partition.

How to create a macOS Catalina installer

1) Download the Install macOS Catalina Beta application.

If you have a paid developer account, you can download the Beta Access Utility from the Apple Developer portal downloads section. Once installed on your computer, it will begin downloading the Developer Beta.

If you don’t have a paid developer account, you can join the Public Beta for free. You will then be provided with a different version of the Beta Access Utility. Once installed on your computer, it will begin downloading the Public Beta.

2) Once the download is finished, your Mac will open it. Quit it, open your /Applications folder and find the installer there. It’s simpler not to rename the file, nor to move it out of /Applications.

3) Format your >=8GB drive to GUID Partition Map and Mac OS Extended (Journaled); this can be done from the Disk Utility application. This will wipe the drive completely.

Erase drive

4) Name the formatted USB drive USB.

5) Now open up Terminal and paste in this command:

sudo /Applications/Install\ macOS\ Catalina\ --volume /Volumes/USB --nointeraction

This will use the Catalina application to create an installer on your chosen drive.

  • If you want to be asked for confirmation before erasing the drive, remove “–nointeraction” from the command.
  • The “–downloadassets” flag was introduced in macOS Mojave. It downloads assets which may be required during installation. This is presumably helpful for faster or offline installations, though I haven’t noticed a difference. I wouldn’t bother with it for the beta installer, but it might be worth it once the general release comes around. The command works fine without the flag included.
  • Older versions of macOS used an “–applicationpath” flag in this command, but this is now deprecated and will cause an error if used. Use the command above, instead of updating the command mentioned in guides which were written for previous versions of macOS.

6) Hit Enter to issue the command, and put in your password when prompted. Terminal will inform you when the drive has been successfully created, and it will appear on the desktop entitled Install macOS Catalina Beta.

How to use the macOS Catalina USB installer

1) Shut down your computer and insert the USB drive.

2) Start the computer whilst holding down the Option (⌥) key.

3) The Startup Manager will show a list of available drives. Select Install macOS Catalina Beta to boot from the USB drive.

4) You can now install macOS Catalina as you like. The installer allows you to reformat your startup drive and other storage disks too. Tools such as Terminal, Startup Disk, and Firmware Password Utility are accessible from the top-bar menus.

Enjoy trying out Apple’s newest offering! Remember that beta software will contain bugs, so if you have critical data on your machine you might be better off installing macOS Catalina to a separate drive.

Your USB install drive can be used to troubleshoot your Mac if it becomes corrupted and can’t make use of its own Recovery partition. The ability to reinstall the operating system or use Terminal from the drive is extremely useful. You can also use it to install Catalina to other computers without having to re-download the installer each time.

Need help with this guide? Ask your questions below!