advixity/Create a MacOS installer USB (on Windows).md

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A (relatively) simple guide to create a Bootable MacOS installer USB on Windows

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Create a MacOS installer USB (on Windows).md

Create a Bootable MacOS installer USB on Windows

Note! Before proceeding, please make sure that you have a USB flash drive at least 8GB in size. All data will be destroyed on this drive, so please back up your files.

1. Obtaining the image

Go to this apple.com support article (10.7 Lion - 10.12 Sierra) and scroll down to "Use a web browser for older versions" Right click your desired OS and click "Save link as". Save the DMG to a folder.
Alternatively, go to this archive.org page for all MacOS images and download your version DMG.

2. Preparing the files

Using a program such as 7-Zip, open InstallMacOSX.dmg
If you don't already have 7-Zip, download it from the link above and run the installer.
Navigate to InstallMacOSX.dmg\Install OS X\InstallMacOSX.pkg\InstallMacOSX.pkg\InstallESD.dmg\OS X Install ESD\
Extract the BaseSystem.dmg, BaseSystem.chunklist and Packages folder to a folder of your choice
Now navigate to InstallMacOSX.dmg\Install OS X\InstallMacOSX.pkg\InstallMacOSX.pkg\InstallESD.dmg\OS X Install ESD\BaseSystem.dmg\OS X Base System\Install OS X El Capitan.app\Contents\Resources\ and extract InstallAssistant.icns
Quit the archiver. We won't be using it anymore.
In your File Manager (Explorer), rename InstallAssistant.icns to ---> .VolumeIcon.icns

3. Creating the install media

Download TransMac (Paid software with Trial) and run the installer.
Insert your desired USB flash drive (8GB+) and run TransMac as Administrator (this will give it the neccessary rights to write to the USB drive.
Wait 10s! and hit "Run"
Select your desired USB flash drive and right-click it. Select Format Disk for Mac
Once finished, right click again, and select Restore with Disk Image
Select your previously extracted BaseSystem.dmg and hit OK
Select Enlarge Volume to Drive Size and press OK
Wait a bit for the files to copy over.
Select your USB drive in the sidebar of TransMac. There should be a folder called "OS X Base System". Click on the folder.
The right window pane should show a folder structure
Go back to your File Manager, and locate and select BaseSystem.dmg, BaseSystem.chunklist and .VolumeIcon.icns
Drag all 3 files to into the right pane of TransMac. They should begin to copy over.
Still in TransMac, navigate to USB-Disk\OS X Base System\System\Installation\
Delete the "Packages" File
Replace this with the "Packages" Folder that we extracted earlier.
Wait for the folder to copy over.
That's it! Eject the USB flash drive and unplug it from your computer.

4. Booting and Installing

Go over to your Mac. Make sure it is shut down.
Plug in the USB flash drive we just created.
While holding the Option (Alt) key, power on your Mac. Keep holding the Option key.
When you see a menu with your USB flash drive on it, release the key.
Select OS X Base System and hit Enter
Follow the installation prompts!

5. Uninstalling and Cleaning (Optional)

TODO

All credit to: https://www.youtube.com/watch?v=_g8naTAC9jA

avanbath commented Sep 23, 2025

@advixity

Thank you, starred! This is much simpler than some of the other guides out there.

Wiggie49 commented Sep 30, 2025 •

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The USB is not bootable created by TransMac app. Tried a couple of times without success. Then I found out a post from Microsoft Tech Community and it worked like a charm:

https://techcommunity.microsoft.com/create-a-macos-bootable-usb-on-windows-10/

bayron808 commented Sep 30, 2025

Just dropped a quick read on your gist — really solid breakdown . I ran into a similar issue before and what finally saved me was UltraDMG. It made creating a bootable macOS USB on Windows way less painful for me, super straightforward compared to fiddling with command lines. If anyone else here is stuck, that tool was a UltraDMG in my case.

Source:
https://www.sysgeeker.com/blog/how-to-create-macos-monterey-bootable-usb-on-windows-10-11.html

Author

advixity commented Oct 1, 2025

Well, looks like Ultra DMG works as well, I’ll give it a try and update my gist. Thanks for contributing!

bayron808 commented Oct 2, 2025 •

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Well, looks like Ultra DMG works as well, I’ll give it a try and update my gist. Thanks for contributing!

Hey, did you get around to testing UltraDMG yet?
Just to share — TransMac is paid and honestly pretty expensive (US $59 for a single user license). UltraDMG is way cheaper and does the same thing when it comes to creating macOS bootable USBs.

And from my own experience, on Windows there really isn’t any free tool that can properly make a Mac bootable installer, so it might be worth replacing TransMac to UltraDMG in your gist. That way people don’t assume they need to spend that much just to get it working.

UltraDMG works great on my Windows 11 laptop:

thestart12 commented Oct 24, 2025 •

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I got an erroring while uploading OS X (A1278; No Osx)

1094 commented Nov 7, 2025 •

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Thank you, so much for sharing!!
I having a hard time figuring out what to do with this laptop since it couldn't seem to connect to Apple's servers.

I had some trouble finding the Packages folder I was supposed to back up (I should have checked the "repacking" part sooner); however, this worked perfectly for me for installing Lion (macOS X 10.7)!

Blender-Uploads commented Dec 6, 2025

i got the Ø symbol error after i selected OS X Base System and hitting enter. do i need to follow the video you linked?

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