Windows 11 will lock the file system on some USB sticks and SD cards in 2027

Microsoft has been warning since October 13, 2026 that Windows will no longer recognize ReFS storage devices in the future. The restriction is set to take effect with the security update in January 2027. This update is expected to be released on January 12, the second Tuesday of the month. An affected USB stick or SD card will then no longer open as usual on a Windows 11 PC. The files stored on it will not be automatically deleted, but Windows will initially be unable to access them.

What are the consequences?

Microsoft developed the ReFS file system as a more modern alternative to NTFS, which Windows has been using for many years. Among other things, ReFS is designed to manage large amounts of data more reliably. However, it is not a common choice for typical USB sticks, and Windows 11 does not support it in all scenarios.

Unfortunately, Microsoft has not given a specific reason for the planned restriction. One possible explanation is compatibility issues: ReFS volumes may cause problems with Windows and other devices or operating systems. However, this is merely a conjecture.

Administrators can bypass the restriction via a Group Policy named ‘RefsRemovableDeviceMountPolicy’ or via an entry in the Windows Registry. These settings are primarily intended for managed computers. Anyone unfamiliar with them should therefore avoid changing them.

Microsoft classifies the use of ReFS on removable media as unsupported. Although the file system can manage partitions of up to 35 petabytes in size — equivalent to 35 million terabytes — this advantage is of little practical relevance for everyday use with USB sticks. Windows 11 can already use ReFS for certain data partitions; however, it is still not intended for use as a standard system partition.

You can find more information about the planned end of support for ReFS in this blog post.