Making a Mac OS USB bootable installer saves much time when you want to install the OS offline on two or more Macs. Also, it helps in restoring a system after a startup failure. It is easy to make Mac OS USB drive from the full installer downloaded from the App store; Apple provides clear-cut instructions for the same. However, people use this feature only when they have a problem with their computer, mainly when their system is not booting up. One needs a Mac for creating this USB disk, but then, what to do if you don’t a have spare Mac? In this post, we explain making bootable macOS USB installer from a Windows PC.
Making bootable Mac OS recovery USB on Windows
TimeMachine is the safest option to recover a broken Mac in the offline mode. If a backup is not there, you have to go for a clean installation either from a bootable USB/DVD drive or the Internet. In my case, I lost the boot partition of my iMac and didn’t have a TimeMachine backup. Internet recovery was showing up, but it kept on failing to download the OS files from the servers. As it is my only Mac, I had no option left, until I found the method to use a Windows PC to create a Mac OS bootable USB installer. I did this for making a macOS High Sierra USB drive, and later I was successful in reinstating my iMac. As of now, the OS is Mojave, but the process given below is compatible with all recent editions of macOS.
Related: Check our page of converting macOS to DMG to learn the official way to make bootable backup USB drive on a Mac.
How to download bootable macOS USB file [ DMG] for Windows.
As said in the beginning, a Mac is must for creating bootable macOS USB disk. . If you are thinking about to do it from Windows, the options are limited. The cross-compatibility of extensions for the two OS are entirely different. Luckily some Windows applications support a bootable macOS disk format, DMG. Hence, If we can download macOS DMG file, then it possible build the USB installer from Windows environment.
Most of the sites talking about the bootable macOS USB installer on Windows is not guiding on how to download the required DMG files for the method. Check our page to download macOS in DMG format for Mojave and High Sierra.
Erasing USB disk on Windows to make it bootable on Mac
Here we are creating a UBS installer for Mac on Windows. So make sure that we keep the partition of the USB disk to have an appropriate scheme. Converting the USB disk to have a GUID partition table (GTP) is recommended for this method work effectively.
Connect the USB disk to Windows and run the above-given commands in the correct order. It cleans and converts the USB disk to GUID partition table if it is using MBR or something else.
Steps to make bootable macOS USB installer on a Windows PC
When the Internet recovery is stuck and fails to download the OS files, you could use Windows to make a bootable macOS USB installer. Out of the two or three software for handling macOS installer [dmg] in Windows, Transmac is the best one. A screenshot of the Transmac version 12.4 for Windows 10 is what you see below.
Transmac is not free, but the developers offer a 15-day trial period, and that is sufficient for one-time use. Now let’s move on to the steps to create macOS recovery USB drive from PC.
- Download Mac OS DMG file. (Check the link above for Mojave and High Sierra DMGs for Windows)
- Install the Transmac 12.4 trial for Windows; download here.
- Prepare the USB drive GUID partition table (GTP) as explained above.
- Right-click on Transmac icon, and select to run it with Admin privileges.
- As shown in the screenshot, right-click on your USB disk and pick the option Restore with Disk Image.
- Point the Windows Explorer to the location where you have the bootable macOS DMG file.
- Wait until the software completes restoring the USB drive with the input.
- The bootable Mac OS USB installer is ready when you see the message “Restore Complete”.
- Safely remove the drive from Windows PC and use it on your Mac.
Check the video below to see our Mac booting-up from the macOS High Sierra USB installer. In this way you could recover and restore a Mac without Internet. Some models of Macs show a prohibitory symbol when you boot from macOS Mojave recovery USB made on Windows. In that case, you need to Install High Sierra first and then upgrade to Mojave using the in-built software updater.
While restarting, Press the Option key on your Magic keyboard or MacBook see the boot choices. However, if you use a Windows keyboard for Mac, press the Alt key. When you see the boot menu, click on the USB disk with label macOS, and proceed to the recovery process as shown in the video.