Make a bootable Windows 11 USB drive from a Mac

Update 2026-05-24: Updated for Windows 11.

This is a quick "how to" guide to make a bootable Windows 11 USB drive/stick on a Mac from an ISO file. If you haven't already done so, you'll need to download the Windows 11 disk image (ISO) file from Microsoft.

The process is straightforward, but requires one third party tool called wimlib and some terminal/command prompt usage.

Preamble: why's it so difficult?

Normally I use etcher for burning ISOs, but a Windows USB installer has special requirements in order to be bootable (it uses a special UEFI boot process).

The approach here is to format the USB drive and copy the files manually. The snag is that the installer requires FAT32, which has a 4 GB per-file limit, and Windows 11's install.wim is over 5 GB. The official Microsoft instructions cover splitting the file, but only from Windows. Here I'll describe how to do it on a Mac using wimlib.

Step 1: Format the USB drive

The first step is to identify the USB drive device name using diskutil list. Make sure you identify the correct USB disk, as entering the wrong device name in the next command could lead to data loss.

Now format the drive as follows, substituting your disk name for diskN:

diskutil eraseDisk MS-DOS "WINDOWS11" MBR diskN

Step 2: Mount the ISO and copy most of the files

Mount the Windows 11 ISO by opening it in Finder. Check the name of the volume in Finder, or in the command prompt:

ls /Volumes

The volume name varies by edition and download – it's something like /Volumes/CCCOMA_X64FRE_EN-US_DV9. Substitute whatever appears on your system in future commands.

Windows 11's install.wim is always over 5 GB, so you'll need to split it. First, copy all files except install.wim to the USB drive:

rsync -avh --progress --exclude=sources/install.wim /Volumes/CCCOMA_X64FRE_EN-US_DV9/ /Volumes/WINDOWS11

Step 3: Download wimlib and use it to split install.wim

wimlib is a free tool for working with .wim files that runs on Mac and Linux¹. Install it via Homebrew (follow that link if you don't have Homebrew yet):

brew install wimlib

Then split install.wim:

wimlib-imagex split /Volumes/CCCOMA_X64FRE_EN-US_DV9/sources/install.wim /Volumes/WINDOWS11/sources/install.swm 3800

The 3800 means the file should be split into 3800 MB-sized chunks (to keep under the 4 GB limit).

Simply eject the WINDOWS11 volume by clicking on the eject symbol in Finder, and remove the USB drive. It's now ready to use as a bootable installation disk.

Finally, if the USB drive won't boot, check that your machine is set to boot in UEFI mode – Windows 11 does not support legacy/CSM BIOS boot. If you have a "legacy boot" or "CSM" option in your BIOS, make sure it is disabled.

Summary

Here, I've covered how to create a bootable USB drive for installing Windows 11 using a Mac and an ISO image downloaded from Microsoft. File this one under "no idea why they make this so difficult"!

Thanks for reading!

Acknowledgements

Thanks to Josh Beam, whose 2017 guide inspired this approach. Thanks also to Parul Jain for the 3800 MB split size suggestion, and to @FingerlessGloves for the updated Homebrew installation command.

1. I've also tried formatting the USB drive as exFAT to avoid the 4 GB limit, but it isn't bootable. ↩