Bootable USB installers offer an easy way to upgrade multiple Macs to macOS Catalina, to perform clean installs of MacOS Catalina, to perform maintenance from a boot disk like formatting disks, modifying disk partitions, and performing restorations, and much more. We’ll walk through how to create a boot USB install drive for MacOS Catalina 10.15. 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.

  1. After macOS Sierra, all the later versions of macOS can be supported by USB 3.0. Install VirtualBox Extension Pack and enjoy using macOS operating system on Windows PC. MacOS Catalina 10.15 Virtual machine image (VMDK File): If you want to use macOS Catalina for Virtualization.
  2. The macOS Catalina installer software is over 8GB, so you need a USB external drive that can hold that much data. The drive can be a thumb drive, hard drive, or SSD.

It does not matter whether you use macOS or Windows 10. It’s just a matter of time until your device will refuse to start, which could happen for many reasons, including (and not limited to) file corruption, hardware failure, and buggy update. If the unexpected happens with an Apple computer, you can use a macOS bootable USB with the installation media to repair it.

This is one of the main reasons you should consider making a macOS bootable USB when your device is working properly. However, if none of your devices (MacBook, MacBook Air, MacBook Pro, iMac, Mac Pro, or Mac Mini) aren’t working when you need them the most, then you can use a PC to rescue your Apple device. You can use a Windows 10, Windows 8.1, or Windows 7 device to quickly create a USB bootable installation media to reinstall macOS Catalina or Big Sur on your Mac.

In this guide, you’ll learn the steps to create a macOS Catalina bootable USB installation on Windows 10, which you can use to reinstall or upgrade the Apple OS.

Requirements

Before proceeding, you’ll need the following:

  • Broken Mac computer running macOS (version 10.12, 11, or later).
  • A trial copy of the TransMac software.
  • One high-quality USB flash drive with 16GB of storage.
  • Copy of macOS (DMG file).

Create macOS bootable USB installation media

To create a bootable USB drive with macOS, use these steps:

  1. Download and install TransMac on the Windows 10 device.

    Quick note: This is a paid software, but it gives you a 15-day trial, which is more than enough time. (If this works for you and you want to support the developer, you can purchase the full version.)
  2. Connect the USB flash drive. (If you have any data on the flash drive, remember to make a backup, as everything on it will be erased.)

  3. Right-click the TransMac app and select the Run as administrator option.

  4. Click the Run button. (If you’re using the trial version, wait 15 seconds.)

  5. Right-click the USB flash drive, select the Format Disk for Mac option from the left navigation pane.

    Quick note: You want to do this before creating the bootable media because there is a good chance that the drive was formatted using a Windows device. If this is the case, the chances are that it’s using an MBR partition, and the USB drive needs a GPT partition to work on a Mac.
  6. Click the Yes button to format the drive on the warning message.

  7. Confirm a name for the drive. For example, “macOS bootable USB.”

  8. Click the OK button.

  9. Click the Yes button.

  10. Click the OK button.

  11. Right-click the USB flash drive and select the Restore with Disk Image option from the left navigation pane.

  12. Click the Yes button to confirm the erase of the USB flash drive data.

  13. Click the browse button on the right.

  14. Select the .dmg file with the macOS installation files.

  15. Click the Open button.

  16. Click the OK button.

  17. Click the Yes button.

Once you complete the steps, you can now insert the USB flash drive on your Mac computer to install, reinstall, or upgrade the operating system to the latest macOS version, which can be Sierra, Catalina, Big Sur, or higher.

Create a GPT partition on USB flash drive

If the USB flash drive is not working with TransMac, it could still be a partition problem. In this case, you may need to redo the entire process again. However, this time you should use the following steps to use the Diskpart command-line utility on Windows 10 to create the appropriate GPT partition, and then follow the above instructions.

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To create a GPT partition on a removable drive, use these steps:

  1. Open Start.

  2. Search for Command Prompt, right-click the top result, and select the Run as an administrator option.

  3. Type the diskpart command and press Enter.

  4. Enter the list disk command to view all drives connected to your computer and press Enter.

  5. Type the select disk command followed the number assigned for the USB flash drive (for example, select disk 4), and press Enter.

  6. Enter the clean command and press Enter.

  7. Type the convert GPT command and press Enter.

  8. Enter the create partition primary command and press Enter to complete the process.

Once you formatted the USB flash drive with a GPT partition, you can use the instructions mentioned above to use TransMac to create a bootable media, but this time skip steps No. 5 through 10 and continue on step 11.

After the process completes, which can take up to an hour, connect the USB flash drive and power on your Mac holding down the Option key, select the USB drive to begin installing macOS.

If you have problems creating the bootable media, you can get a USB flash drive that comes with macOS Sierra, El Capitan, Catalina, etc., on it with the link mentioned below. (I haven’t tried it personally, but it’s worth the try if nothing works.)

Adapter

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 8.09GB 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.

Get an external drive and maybe an adapter

The macOS Catalina installer software is over 8GB, so you need a USB external drive that can hold that much data. The drive can be a thumb drive, hard drive, or SSD.

If you have a 2015 or newer MacBook or a 2016 or newer MacBook Pro, you may need Apple’s $19 USB to USB-C adapter. This will allow you to connect a storage device that uses a USB type-A connector. If you don’t have an external drive and you have a USB-C Mac laptop, you could buy the SanDisk Ultra USB Type-C Flash Drive, which has a USB-C connector. You can get model number SDCZ450-016G-G46.

When creating the boot drive, the storage device is reformatted, so there’s no need to format the drive beforehand.

Get the macOS Catalina installer software

The macOS Catalina installer is available in the App Store. If you launch the App Store app, do a search for “Catalina.” Or, if you click this Catalina App Store link, it will take you to the Catalina App Store webpage, then click on the “View in the Mac App Store” button.

You can read the information to learn more about Catalina. When you’re ready to download the software, click the Download button. (If you’ve already downloaded the installer, the button will say Install instead of Get.)

Bootable macos catalina usb 3.1

Once the download is complete, the installer will launch automatically. But don’t continue with the installation. Instead, press Command-Q on your keyboard to quit the installer.

The Catalina installer app will be in your Applications folder, so you can go there and launch it later to upgrade your Mac to the new operating system.

Make a bootable installer drive: The quick way

I used a free app called Install Disk Creator to make the installation drive. Download Install Disk Creator by clicking on the link. When the download is done, you can move it over to your Applications folder. Then follow these steps to create your bootable macOS Catalina drive.

1. Connect your drive to your Mac.

Make Bootable Usb Os X Catalina

2. Launch Install Disk Creator.

Bootable macos catalina usb adapter

3. In the main window, you’ll see a pop-up menu under Select the volume to become the installer. Click on the menu and select your drive.

Bootable Macos Catalina Usb 3.1

4. Under the pop-up menu, you’ll see Select the OS X installer. (macOS used to be called OS X.) If you have only the Catalina installer on your Mac, Install Disk Creator will automatically select it. If you have other macOS installers, you need to click on Select the OS X installer and select the Catalina installer.

5. When you’re ready, click Create installer. Your Mac may tell you that Install Disk Creator wants to make changes, and you need to enter your user name and password. After you do this, the app will take a few minutes to create the boot drive. A progress bar. appears at the bottom of the Install Disk Create window.

If you try to start the process and you get a failure message saying that the drive couldn’t be unmounted, try reformatting the drive first as ExFAT using Disk Utility. Then start the process over again.

Bootable Macos Catalina Usb

Mac

When the app is done, the installer is ready to use.

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