How To Create A Bootable Installer For Macos High Sierra

It does not matter whether you use macOS or Windows 10 (or Windows 11). 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 works properly. However, if none of your devices (MacBook, MacBook Air, MacBook Pro, iMac, Mac Pro, or Mac Mini) are not 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 Monterey, Big Sur, or Catalina on your Mac.

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

Requirements
Create macOS bootable USB installation media
Create GPT partition on a USB flash drive

Requirements

Before proceeding, you'll need the following:

Broken Mac computer running macOS (version 10, 11, 12, or higher).
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:

Download and install TransMac on Windows 10.

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.)
Connect the USB flash drive. (If you have any data on the flash drive, remember to create a back it up, as everything on the drive will be erased.)
Right-click the TransMac app and select the Run as administrator option.
Click the Run button. (If you use the trial version, wait 15 seconds.)

TransMac on Windows 10
Right-click the USB flash drive, select the Format Disk for Mac option from the left navigation pane.

Format Disk for Mac using GPT partition

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.
Click the Yes button to format the drive on the warning message.

Format warning
Confirm a name for the drive. For example, "macOS bootable USB."
Click the OK button.

Format USB for macOS with label
Click the Yes button.

Overwrite warning
Click the OK button.
Right-click the USB flash drive and select the Restore with Disk Image option from the left navigation pane.

TransMac Restore with Disk Image option
Click the Yes button to confirm the erase of the USB flash drive data.

Delete warning
Click the browse button on the right.
Select the .dmg file with the macOS installation files.

Select dmg macOS file to create a bootable USB drive
Click the Open button.
Click the OK button.
Click the Yes button.

TransMac creates a macOS USB bootable drive warning.

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, Monterey, or higher.

Create a GPT partition on a 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.

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

Open Start.
Search for Command Prompt, right-click the top result, and select the Run as an administrator option.
Type the diskpart command and press Enter.
Enter the list disk command to view all drives connected to your computer and press Enter.
Type the select disk command with the number assigned for the USB flash drive (for example select disk 4) and press Enter.
Enter the clean command and press Enter.
Type the convert GPT command and press Enter.
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.