Microsoft's Resilient File System (ReFS) was introduced in 2012 with Windows Server 2012 and has been relatively obscure compared to NTFS. It has recently emerged as an optional feature in a preview build of Windows 11 (Build 27823), allowing users to format partitions with a "Flexible Storage" option, offering a choice between NTFS and ReFS. ReFS is designed for larger storage capacities, can format partitions up to 35 petabytes, and supports single files as large as the entire volume. It includes advanced features like block cloning and file-level snapshots but lacks support for certain NTFS functionalities such as bootable volumes and file compression. Currently, ReFS is primarily aimed at enterprise and server environments, but its inclusion in Windows 11 may indicate plans for broader consumer access. The open-source community is developing unofficial documentation for ReFS, and Paragon Software has created a closed-source ReFS driver.