Create Windows 10 Bootable USB on Mac OS

• Download Windows 10 ISO file from https://www.microsoft.com/en-us/software-download/windows10
• Insert a USB drive with more than 16GB capacity.
• Identify the device name of the USB drive using

  diskutil list

  It should something like e.g. /dev/disk2
• Format the USB drive:

  diskutil eraseDisk MS-DOS "WIN10" GPT /dev/disk2

• Mount Windows 10 ISO:

  hdiutil mount ~/Downloads/Win10_1903_V1_English_x64.iso

• Copy files from Windows 10 ISO to the USB drive:

  rsync -vha --exclude=sources/install.wim /Volumes/CCCOMA_X64FRE_EN-US_DV9/* /Volumes/WIN10

• Install wimlib:

  brew install wimlib

• Use wimlib-imagex to split install.wim to 3.8GB swm files:

  mkdir /Volumes/WIN10/sources

  wimlib-imagex split /Volumes/CCCOMA_X64FRE_EN-US_DV9/sources/install.wim /Volumes/WIN10/sources/install.swm 3800

• Done

see also

• How to Make a Windows 10 USB Using Your Mac - Build a Bootable ISO From Your Mac's Terminal