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[Bug]: exfat option in Make2023BootableMedia.ps1 results in non-bootable USB #424
Description
Is there an existing issue for this?
- I have searched existing issues
Current Behavior
Using -FileSystem ExFAT when attempting to make a bootable USB results in a non-bootable USB. This seems to happen because most UEFI firmware does not support ExFAT by default.
Although FAT32 is the default, it doesn't work for larger partitions and the script recommends to use ExFAT in that case.
Expected Behavior
Using the script should result in a bootable drive, so the ExFAT option should not exist unless there is some way to make it bootable on most computers.
Steps To Reproduce
- Tested with Windows 11 with Secure Boot enabled and updates applied, using a 256 GB USB stick with a GPT partition table and a single partition covering the whole drive. The ISO used was Win11_25H2_English_x64_v2.iso.
- Run
.\Make2023BootableMedia.ps1 -MediaPath C:\Media\Win11_25H2_English_x64_v2.iso -TargetType USB -USBDrive E: -FileSystem ExFAT(adjusting the command to point to the correct paths). The script should not display any errors at this stage. - Attempting to boot from the USB will likely fail as UEFI firmware is not required to understand ExFAT.
Build Environment
- OS: Microsoft Windows [Version 10.0.26100.8457]
Bug report is for a script, so I didn't build/compile anything, just downloaded it.Version Information
Tag: v1.6.4-signed
Urgency
Low
Are you going to fix this?
Someone else needs to fix it
Do you need maintainer feedback?
No maintainer feedback needed
Anything else?
There is a message in the script saying that the filesystem must be FAT32 to boot on most UEFI systems but the actual code still allows ExFAT so that error will never actually display if -FileSystem ExFAT is used.
Log:
.\Make2023BootableMedia.ps1 -MediaPath C:\Media\Win11_25H2_English_x64_v2.iso -TargetType USB -USBDrive E: -FileSystem ExFAT
Microsoft 'Windows UEFI CA 2023' Media Update Script - Version 1.4
WARNING: Contents on drive [E:] will be erased! Continue? (Y/N)
y
Initializing staging directory
Staging media
Mounting ISO from staged media
Mounting boot.wim from staged media
Updating staged media to use boot binaries signed with 'Windows UEFI CA 2023' certificate
Creating 'Windows UEFI CA 2023' bootable USB media on drive [E:]
Successfully created media on drive [E:]
Activity
ballsop commentedon May 29, 2026
May (@ave9858) to be clear, the ask is to just add clarification when using -ExFAT that it is unlikely to work on most systems today? There is no way to know what the target system supports. So best we can do here is warn the user (or deprecate the support since it is very rare).
ave9858 commentedon May 29, 2026
Yes, currently the script doesn't warn against using ExFAT and even recommends it when the target partition is bigger than 32 GB.
mu-automation commentedon Jul 13, 2026
This issue has been automatically marked as stale because it has not had activity in 45 days. It will be closed if no further activity occurs within 7 days. Thank you for your contributions.
ave9858 commentedon Jul 14, 2026
I don't think the script has been updated
mu-automation commentedon Aug 29, 2026
This issue has been automatically marked as stale because it has not had activity in 45 days. It will be closed if no further activity occurs within 7 days. Thank you for your contributions.
ave9858 commentedon Aug 30, 2026
I don't understand the purpose of this bot
mu-automation commentedon Oct 14, 2026
This issue has been automatically marked as stale because it has not had activity in 45 days. It will be closed if no further activity occurs within 7 days. Thank you for your contributions.
ave9858 commentedon Oct 15, 2026
👎