This article guides you through the process of performing a clean installation of macOS 10.15 Catalina using the bootable USB drive method, rather than upgrading your Mac using Apple's standard installation package, which retains existing user data and any user-installed apps.

macs macos catalina
Creating a bootable USB drive provides you with a convenient way to install a fresh copy of macOS Catalina on multiple Macs. Performing a clean install can also remove annoying quirks and strange behaviors that your Mac may have inherited over time, and often helps to reclaim disk space caused by junk files left by third-party apps.

To follow the steps in this article, you'll need an empty 16GB or larger USB thumb drive (USB-C or USB-A, depending on your Mac) and an hour or two of downtime while the installation procedure completes.

Also, be sure to perform a full backup of your Mac beforehand using Time Machine, so that you can restore your original system from the Recovery partition if something goes wrong.

Compatibility Check

macOS Catalina is a major update that introduces a range of new features and changes including cross-platform app support for third-party apps, no more iTunes, iPad as a second screen functionality, Screen Time, and more.

Every Mac that can run macOS Mojave will run macOS Catalina, with the exception of the mid-2010 and mid-2012 Mac Pro models. The full list of compatible Mac models is as follows:

  • MacBook (Early 2015 or newer)
  • MacBook Air (Mid 2012 or newer)
  • MacBook Pro (Mid 2012 or newer)
  • Mac mini (Late 2012 or newer)
  • iMac (Late 2012 or newer)
  • ‌iMac‌ Pro (2017)
  • ‌Mac Pro‌ (Late 2013)

To check if your Mac is compatible, open the Apple () menu in the upper left corner of your Mac's screen and select About This Mac. Look just below the OS X version number in the Overview tab – if the Mac model name is the same or a later model year than the one shown in the compatibility list above, your Mac is compatible with macOS Catalina.

How to Perform a Clean Install of macOS Catalina

  1. Download macOS Catalina from the Mac App Store [Direct Link].
    Mac App Store

  2. Once the download is complete, close the installer window by selecting the Quit Install macOS option in the menu bar or using the keyboard shortcut Command (⌘) + Q.
  3. Launch the Terminal app (found in Applications/Utilities/Terminal).
  4. At the Terminal command prompt, type sudo followed by a space.
    mojave clean install 2

  5. Next, open a Finder window, navigate to your Applications folder, right-click (or Ctrl-click) on the macOS 10.15 installer, and select Show Package Contents from the contextual dropdown menu.
  6. Navigate to Contents -> Resources within the installer package.
  7. Drag the createinstallmedia file into the Terminal window.
    mojave clean install 4

  8. Still in the Terminal window, type /Applications/Install\ macOS\ Catalina.app/Contents/Resources/createinstallmedia --volume /Volumes/XXXXX but replace XXXXX with the name of the USB drive you intend to use as a bootable installer.
  9. Once you've replaced XXXXX in the last step with the name of the USB drive, press the Enter key on your keyboard to run the completed Terminal command.
  10. Enter your administrator password when prompted.
  11. Type Y and press Enter when prompted, and the command will create your bootable Catalina installer on the USB drive. This will take a few minutes to complete, so leave it running until you see the message "Install media now available." Note that if you're asked whether you want to install Xcode during the process, you can safely click Not Now and the process will complete successfully regardless.

Restart and Install

You can install Catalina on your Mac as soon as the USB installer has been created. To do so, restart your Mac and hold down the Option (⌥) key as soon as you hear the reboot tone. Then follow these steps:

  1. Use the mouse pointer or the arrow keys on your keyboard to select the disk called Install macOS Catalina in the drive list that appears on the screen.
  2. Once the USB drive has booted, select Disk Utility from the Utilities window, choose your Mac's startup drive from the list, and click Erase.
  3. When your Mac's startup disk is formatted, return to the Utilities window and select Install macOS, choose your freshly erased startup drive when asked where to install the OS, and follow the onscreen prompts to complete the installation.

To install Catalina on another Mac, first make sure it's powered off, then simply plug in the USB installer you created and turn the Mac on. When you hear the boot tone, hold down the Option (⌥) key and follow the three steps above.

(Thanks to Angus for the new Terminal command!)

Top Rated Comments

The Weatherman Avatar
21 months ago
Or you can use the more straightforward Internet Recovery method ('https://wccftech.com/how-to/how-to-clean-install-macos-catalina-without-usb-using-internet-recovery-tutorial/').
Score: 10 Votes (Like | Disagree)
TarnishedTinMan Avatar
21 months ago
I am not sure the process in the article works with any of the T2 security chip Macs. (My 2019 MacBook Pro among them)

On those units, the T2 controls the ability to boot from an external drive. To be able to boot off the external drive you have to authenticate as an administrator. That step was left out of the instructions.

In regards to the Internet Recovery method, mentioned in the comments, that will recover you to the OS that was last installed on the Mac, not install a new one.

One more thing, if you erase the main drive and then reboot with a T2 Mac you will have to authenticate as an administrator as I already mentioned to boot off the USB drive, but the Mac looks at the boot drive for administrators that you can log into the security menu to boot from the external drive. Erased boot drive so no known administrators, so no way to boot off the USB drive. (Only a small amount of panic at this point)

What I ended up having to do was the Internet Recovery method, which is how I know it will only allow you to install the last installed OS. Then I installed Catalina over that fresh install of Mojave.

Then booted from the USB drive again, formatted the drive again, rebooted and used internet recovery to install the last installed version of the OS which now was Catalina.

If you are curious about the T2 chip, this white paper helped me to figure out what to do once I was hosed with no administrator:

https://www.apple.com/mac/docs/Apple_T2_Security_Chip_Overview.pdf

If you don't trust the link, search on "Apple_T2_Security_Chip_Overview" and that will pull the article up too.

I am sure there is a more elegant way to accomplish this same thing when a T2 chip is involved. Hopefully someone will write about it after they do it.
Score: 7 Votes (Like | Disagree)
pika2000 Avatar
21 months ago
I don't understand why it's so complicated nowadays to do an offline clean install.

In contrast, Microsoft is making it ultra easy to do an offline clean install of Windows 10 by providing a straightforward utility to create a generic Windows 10 bootable USB that can be used to install any version of Windows 10. Wish Apple would do the same.
Score: 5 Votes (Like | Disagree)
konqerror Avatar
21 months ago

In regards to the Internet Recovery method, mentioned in the comments, that will recover you to the OS that was last installed on the Mac, not install a new one.
No. Command-option-r will load the latest OS compatible with the Mac. It does take a little while for Apple to update the recovery image after release, but it is working now.

https://support.apple.com/en-us/HT204904
Score: 4 Votes (Like | Disagree)
ipedro Avatar
21 months ago
I've got so much cruft from years of installs on top of installs that I may yet go for a clean install. Looking through my apps and finding a bunch of old 32Bit apps that I can't use anyway, it might be a good excuse to start over, with only 64bit apps.
Score: 4 Votes (Like | Disagree)
pj-uk Avatar
21 months ago

It is amazing how people complicate things to install macOS including third-party applications like “Install Disk Creator”, “DiskMaker X” or similar; and even Terminal commands. It is much easier than that. Just 1-2-3:

1. Download the macOS installer and open it.
2. Select the desired destination disk and install.
3. Boot from such disk.

That is! No Terminal commands needed. No third-party applications needed either. The Mac way!
If you read the article it says "How to Perform a Clean Installation of macOS 10.15 Catalina"...not an update.


After I do a clean installation I will login to my iCloud and App Store accounts. Will it bring back stuff from 2014 in keychain app?

Because I want them to gone, Safari auto fill passwords are good enough for me.
Yes it will. You can always back-up keychain if you want to.
Score: 3 Votes (Like | Disagree)

Top Stories

General Music and AirPod 3 Feature

Rumor: Apple to Announce Third-Generation AirPods and HiFi Apple Music Tier on May 18

Thursday May 13, 2021 10:32 pm PDT by
A new rumor suggests that Apple will announce the third-generation AirPods and the recently rumored HiFi, or high-fidelity Apple Music tier, on Tuesday, May 18, via a press release on its website. The new rumor comes from Apple YouTuber Luke Miani who shared the alleged exclusive news with the AppleTrack website. According to the YouTuber, Apple plans to release the next-generation AirPods...
apple park drone june 2018 2

Apple Fires Newly Hired Ex-Facebook Product Manager Following Revelations of Past Misogynistic Comments

Thursday May 13, 2021 12:10 am PDT by
Apple has fired Antonio García Martínez, an ex-Facebook product manager and author of the controversial book "Chaos Monkeys," following public and internal calls for removal and investigation due to past misogynistic statements, The Verge reports. Apple hired Martínez earlier this week to join its ads team, however, comments that Martínez made in the past sparked condemnation from users...
imac m1 blue isolated 16x9 500k

M1 iMac is Up to 56% Faster Than Prior-Generation High-End 21.5-Inch iMac

Wednesday May 12, 2021 10:03 am PDT by
Apple's M1 iMacs are set to start delivering to customers next week, and ahead of the official launch day, benchmarks for the machines have been showing up on Geekbench, likely from reviewers who are testing them. It will come as no surprise that M1 iMac benchmarks are right on par with benchmarks for the M1 MacBook Pro, MacBook Air, and Mac mini, coming in with an average single-core score...
2021 mbp hdmi slot 3d

2021 MacBook Pro Leaks Confirm Returning MagSafe and Ports

Friday May 14, 2021 3:06 am PDT by
Apple's upcoming MacBook Pro models are expected to feature a number of major changes such as larger display options and powerful new Apple silicon chips. Among the more surprising updates to this year's MacBook Pro models is the return of three ports that have been missing from the machines for over five years. Expected to come in 14- and 16-inch sizes, the 2021 MacBook Pro models are...
fortnite apple logo 2

Judge in Epic vs. Apple Case Floats Potential Compromise

Wednesday May 12, 2021 3:54 pm PDT by
In the ongoing legal battle between Apple and Epic Games, the two companies are this week calling up their expert witnesses to argue their points before Judge Yvonne Gonzalez Rogers, who will make a decision in the case after a three week trial. Expert testimony is not as exciting as some of the leaked App Store documents that were highlighted last week, especially as much of what's being...
google photos

PSA: Google Photos Unlimited Storage Ends Next Month, Here's How to Export Your Pictures to iCloud

Thursday May 13, 2021 5:26 am PDT by
For as long as it's existed, Google Photos has offered free unlimited storage for uploading images at a reduced yet good enough quality for most users. From June 1, 2021, however, all photos and videos uploaded to Google accounts will count against users' cloud storage. If you've been relying on Google to back up your media library, it may be time to move that content elsewhere. This article...
AirTag in Envelope Feature 2

AirTag Used to Successfully Track a Mailed Package Across the UK

Wednesday May 12, 2021 8:44 am PDT by
An Apple customer in the United Kingdom has successfully used Apple's Find My network to track an AirTag as it was being sent by mail to a friend in a completely different city. Outlined in a blog post at Intego, Kirk McElhearn said he taped an AirTag to a piece of card, wrapped it inside a small bubble envelope, and then sent it on its way. Kirk lives in the small town of...
m1 ipad pro chip

M1 iPad Pro Over 50% Faster Than Previous Generation in Early Benchmarks

Tuesday May 11, 2021 11:56 am PDT by
Last month, Apple introduced a new iPad Pro with the same M1 chip found in the latest Macs, and early benchmark results indicate that the M1 iPad Pro is over 50% faster than the previous-generation iPad Pro. Based on five legitimate Geekbench 5 results (here's the fifth) for the fifth-generation 12.9-inch iPad Pro with the M1 chip, the device has average single-core and multi-core scores of...
prosser macbook air colors stacked

Images Reveal Colorful New MacBook Air Design

Tuesday May 11, 2021 5:06 am PDT by
Apple's next MacBook Air will feature a completely new design and come in a range of colors like the 24-inch iMac, according to leaker Jon Prosser, who has now released supposedly accurate renders of the new machines based on leaked images. In a new video uploaded to YouTube channel Front Page Tech, Prosser elaborated on his previous prediction that Apple's next-generation MacBook Air models ...
iPhone 13 Camera Backs

iPhone 13 Models Will Be Slightly Thicker and Will Have Larger Camera Bumps

Monday May 10, 2021 10:41 am PDT by
Apple's upcoming iPhone 13 models will be slightly thicker than the iPhone 12 models and will also feature larger, thicker camera bumps with lenses that protrude less, according to iPhone 13 schematics seen by MacRumors. The new iPhone 13 and 13 Pro models are expected to feature a thickness of 7.57mm, up from 7.4mm in the iPhone 12 models. That's an increase of 0.17mm, which won't be hugely ...