Create bootable Windows 10/11 USB drive on Mac OS

Creating a universal bootable Windows Installation USB drive on Mac OS is straightforward. The only pitfall is you have to format your drive as FAT32 to maximize compatibility, but then you have to split your .WIM file to smaller chunks than 4GB so that it does not get corrupted. Fear not, I will guide you through the process. Big thanks to this comment by m13253 for most of the heavy-lifting of this Gist.

Here are the steps (assume your FAT32 formatted USB drive is mounted on /Volumes/USB and your ISO is named something like Win10_1903_V1_Germal_x64.iso):

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❗Preparation:❗ Format your USB drive as FAT32 using Disk Utility on Mac OS!

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1. Download Windows 10 or Windows 11 ISO image from official Microsoft Site. e.g. here is the German ISO for Windows 10.

2. Install Homebrew

   /bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"

3. Install Unetbootin, 7-Zip and wimlib.

   brew install p7zip wimlib && brew install --cask unetbootin

4. Start Unetbootin, select your FAT32 Formatted USB drive and your downloaded ISO File. Let Unetbootin put the ISO file onto the drive.

5. Remove the half-copied .wim file from the USB drive

   rm /Volumes/USB/sources/install.wim

6. Extract install.wim from the ISO to somewhere else.

   cd ~/Downloads
   7z e Win10_1903_V1_Germal_x64.iso sources/install.wim

7. Split install.wim into two parts, each part roughly 3 GiB. According to Microsoft, you can split install.wim into multiple install*.swm files, so they can fit in a FAT32 volume.

   wimsplit ~/Downloads/install.wim /Volumes/USB/sources/install.swm 3072

8. Done!