Windows 11 will block ReFS on USB drives starting January 2027

Microsoft confirmed that with the January 2027 security update, Windows 11 will stop mounting ReFS volumes on removable media by default. The October 2026 update already logs a warning (Event ID 524) without blocking the drive. Admins can override the restriction via Group Policy or the registry.

• ReFS on USB drives will be blocked by default from January 2027
• October 2026 update only warns, logging Event ID 524
• Group Policy or registry can re-allow ReFS on removable media
• Blocking affects mounting only; files are not deleted