Microsoft to block ReFS on Windows 11 USB drives by 2027

Microsoft plans to change how Windows 11 handles the Resilient File System (ReFS) on removable storage devices. Starting with a cumulative update in October 2026, the operating system will enter an audit phase, monitoring and logging the use of ReFS on USB drives via Event ID 524 in the Windows Event Viewer.

By January 2027, Microsoft will implement a security update that blocks the default mounting of external drives and USB sticks formatted with ReFS. While the data will remain physically present on the devices, the system will no longer automatically open them in File Explorer. Microsoft stated that ReFS has never been officially supported for removable media and cited security reasons for the restriction.

Users who require access to ReFS-formatted external drives after the deadline will need to manually adjust system settings through the Registry or Group Policy to bypass the block.