NTFS (New Technology File System) is the standard file system of Windows NT, including its later versions Windows 2000, Windows XP, Windows Server 2003, Windows Server 2008, and Windows Vista.

NTFS supersedes the FAT file system as the preferred file system for Microsoft’s “Windows”-branded operating systems. NTFS has several improvements over FAT and HPFS (High Performance File System) such as improved support for metadata and the use of advanced data structures to improve performance, reliability, and disk space utilization, plus additional extensions such as security access control lists (ACL) and file system journaling. The exact file system specification is a trade secret, although (since NTFS v3.00) it can be licensed commercially from Microsoft through their Intellectual Property Licensing program.

NTFS has five released versions: (the alternate names are due to the fact that the OS version is sometimes set in line with the NTFS version)

* v1.0 with NT 3.1, released mid-1993
* v1.1 with NT 3.5, released autumn 1994
* v1.2 written by NT 3.51 (mid-1995) and NT 4 (mid-1996) (occasionally referred to as "NTFS 4.0", because OS version is 4.0)
* v3.0 from Windows 2000 (occasionally "NTFS V5.0")
* v3.1 from Windows XP (autumn 2001; occasionally "NTFS V5.1"), Windows Server 2003 (spring 2003; occasionally "NTFS V5.2"),Windows Vista (mid-2005) (occasionally "NTFS V6.0") and the upcoming Windows Server 2008

V1.0 and V1.2 are incompatible: that is, volumes written by NT 3.5 cannot be read by NT 3.1.[6] V1.2 supported compressed files, named streams, ACL-based security, etc. V3.0 added disk quotas, and reorganized security descriptors so that multiple files which use the same security setting can share the same descriptor. V3.1 added encryption, sparse files, reparse points, USN journaling, the $Extend folder and its files, expanded the MFT header with a redundant record number useful for recovering damaged MFT files.

Windows Vista introduced Transactional NTFS, NTFS symbolic links, and self-healing functionality though those owe more to additional functionality of the operating system than the file system itself. Yet the NTFS version number has not been raised.