Windows to block ReFS-formatted USB drives by default from January 2027

Microsoft will block mounting of ReFS-formatted USB drives and external storage by default on Windows 11, Windows 10 and Windows Server starting January 2027. Since October 13, 2026, affected volumes are only logged under Event ID 524; drive contents are not erased. Admins can override the restriction via the RefsRemovableDeviceMountPolicy setting.

• From October 13, 2026 Windows only logs ReFS volumes under Event ID 524
• From January 2027 mounting is blocked unless an administrator overrides it
• RefsRemovableDeviceMountPolicy: 0 disables, 1 audits, 2 blocks affected volumes
• FAT32, exFAT and NTFS drives are unaffected and data is not erased