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How to install macOS on an external drive

How to install macOS on an external drive

If you are involved about updating your Mac to macOS Catalina (maybe due to incompatible software program), or if you happen to’re testing a beta model of macOS Catalina and you do not need to threat ruining your system, do not install the replace on your Mac in any respect – you possibly can install it on an external onerous drive as a substitute.

Installing the Mac working system on an external drive is the most secure method to look intently at a new working system without altering something on your Mac. It leaves your present configuration intact and you may play with Catalina or attempt out a beta model.

In this tutorial, we clarify how to run macOS from an external drive.

What you want

If you possibly can, you may need to use a quick drive – it is price investing in a USB C or Thunderbolt 3 drive because it affords the quickest connection. If not, not less than be sure you go for flash storage.

That drive requires not less than 12 GB of space, however, more is really helpful, actually once we began working Mojave beta on a 32 GB stick we discovered it wasn’t sufficient once we began iCloud Desktop and different options which meant that our files began downloading.

If you need to use the distant install as if you happen to had been utilizing it on your Mac, we suggest shopping for the most important USB C / Thunderbolt 3 drive you possibly can afford.

Check out our guide to the perfect external drives for Mac for purchasing recommendation.

Install MacOS on an external drive

Step 1: Prepare for the set up

Follow these directions to put together your external drive:

  1. Connect the external onerous drive to your Mac.
  2. Start Disk Utility (press Cmd + Spacebar and begin typing Disk Utility).
  3. Before this subsequent step – if you’re utilizing High Sierra or later, you will have to click on on the Show drop-down checklist beneath the decrease buttons. Choose Show All Devices from the choices. Now you will notice the external root drive subsequent to the quantity beneath it.
  4. Select the foundation drive within the sidebar (the subsequent step will not do if you happen to solely choose the quantity).
  5. Click on Clear.
  6. Choose Mac OS Extended (Journaled) because the format.
  7. Choose GUID partition map because the scheme.
  8. Name your disk akin to “macOS Catalina” or “USB”.
  9. Click on Clear.
  10. Wait whereas Disk Utility creates the partition and units up the disk (this will likely take a number of minutes).
  11. Then click on Done.

Step 2: Download the macOS set up data

This course of relies upon on whether or not you need to use the beta or a full model of macOS and even an older Mac OS X.

To download the Catalina installer, you possibly can open System Preferences> Software Update. Your Mac searches for the newest software program earlier than providing to download it. You may click on this link to go to the Catalina web page within the Mac App Store. Note that at this stage you solely need to download the software program and never install it.

If you are searching for a full model of an older model of macOS, here is how to download the macOS set up data.

If you might be searching for a beta model of macOS, now we have an entire guide to get the macOS beta right here.

For instance, to download the Catalina beta, you want to do the next:

  1. Register as a developer or for the general public beta program.
  2. After finishing the above step, you possibly can download the Public Beta Access Utility (or Developer Beta Access Utility) from the Apple web site.
  3. The Beta Access Utility DMG file will ultimately seem in your Downloads folder. When it arrives, open it and click on macOSPublicBetaAccessUtility.pkg to install it (it is 215ok).
  4. You may have to enroll your Mac. To check in case your Mac is enrolled, open System Preferences> Software Updates (in earlier variations of MacOS, App Store). If your Mac is enrolled, you will notice “Your computer is set to receive beta software updates.”

    Enroll Mac for beta

  5. Once the Beta Access Utility is put in, the Software Update device will open and the beta will download. (If you might be utilizing an older model of macOS, you’ll be redirected to a Catalina web page within the Mac App Store – you’ll not see this if you’re not registered and use the entry utility). Click Download and wait whereas it downloads to your Mac. The download could take some time as a result of the file is bigger than 5 GB, however, try to be in a position to proceed working whereas the download is happening.


  6. Once the download is full, your Mac will begin it up. WARNING: You do not intend to install it on your Mac, so DO NOT CLICK CONTINUE. Exit the installer as a substitute.
  7. You can find the installer ‘Install macOS Catalina Beta’ in your Applications folder.

Step 3: Install macOS on the external drive

Now install the beta or various model of the Mac working system on your external drive.

  1. Open a search window, go to Applications and find the Catalina Beta installer (or no matter model of macOS you need to use).
  2. Click on the installer.
  3. In the primary window, click on Continue to set up the set up of macOS Catalina Beta (or no matter).
  4. Agree to the software program license settlement.
  5. The n, and that is necessary, click on Show All Disks. Don’t click on Home as a result of you do not need to install on your main drive.
  6. Click on the external drive.

  7. Click Install.

Wait whereas the model of macOS is put in on the disk. This course of could take some time – if it tells you it takes 10 minutes, it’s mendacity.

Note: This is not going to work when you have not set up your external drive as a GUID partition.

Step 4: Run macOS on the external drive

There are 2 methods to run the model of macOS out of your external drive

1 of each:

  1. Open System Preferences> Startup Disk.
  2. Select the external drive you need to use to begin up the Mac and click on Restart.


  1. Hold down Option / Alt throughout startup.
  2. Choose the drive you need to use to boot the Mac.

For more recommendation on putting in macOS or Mac OS X, read How to replace the Mac working system and How to install previous variations of OS X on a Mac.

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