What is the BKF file format?
.bkf is the file format used for backup copies created with Windows Backup Tool (NTBackup) included in MS Windows systems from Windows NT 4.0 through Windows XP Pro and Windows Server 2003. .bkf files store a catalogue containing at least one file chosen by the user for backup. They are also known as NTBackup files or MTF backup files, since the format is built on Microsoft Tape Format (MTF) - a streaming binary container originally designed for tape media.
The purpose of .bkf files is to securely store data backup copies and restore them in case of data corruption or loss. Every .bkf file begins with the four-byte ASCII signature TAPE at byte offset 0, followed by a series of MTF descriptor blocks (TAPE, SSET, VOLB, DIRB, FILE) that stream the archived content.
BKF file features
A .bkf file can store all types of data supported by Windows NT - folders, files, multimedia, and system-state data. NTBackup was removed starting with Windows Vista; to restore a .bkf on Vista or Windows 7, Microsoft released the standalone Windows NT Backup - Restore Utility (ntbackup.msi, KB974674). On Windows 8, 10, and 11, third-party tools such as DataNumen Advanced BKF Repair or SysTools BKF Recovery can open .bkf files directly. Windows Vista and later replaced .bkf with VHD-based backups.
Data in binary format
All data in a .bkf file is saved in binary (little-endian) format and can be examined with a dedicated editor, which will also display properties of the stored backup, including information about:
- type of copy
- tool used to create the copy
- date and time of backup process initiation and completion
Security & safety
RISK: LOWA .bkf is a passive backup container - it doesn't execute. The real risks are practical: aging .bkf files are frequently corrupted (MTF has weak integrity), so keep the original and work on a copy when repairing. Restored content carries whatever risk the original files did (e.g. old executables/macros). Be cautious with 'free BKF opener' downloads - many are trial-only repair tools or adware; Microsoft's NTBackup Restore Utility is the legitimate free option.
Format details
in a nutshellPrograms that open BKF files
Windows5 apps
NTBackup (Ntbackup.exe)
Built-in On Windows XP/2000/Server 2003: Start → Run → ntbackup, choose Restore, pick the .bkf. Native tool on those OSes only.
Windows NT Backup - Restore Utility (NTBackup Restore)
Free Free Microsoft tool for Vista/7 (KB974674): install, run, browse the .bkf and restore files. On Win8/10/11 enable the legacy Removable Storage Manager component first or use a third-party reader.
Veritas / Symantec Backup Exec
Paid The lineage NTBackup came from - reads MTF .bkf in enterprise restore workflows.
DataNumen Advanced BKF Repair
Paid Repairs and extracts files from corrupted/unreadable .bkf when NTBackup Restore fails. Free demo previews recoverable data.
SysTools BKF Recovery
Paid Reads/repairs .bkf on modern Windows and extracts files without needing NTBackup; demo shows preview. Technical details
deep spec| Container format | Microsoft Tape Format (MTF) version 1.0 |
| File signature (magic bytes) | 54 41 50 45 hex ("TAPE") at byte offset 0 - MTF media header descriptor block |
| Byte order | Little-endian |
| MTF block types | TAPE (media header), SSET (data set), VOLB (volume), DIRB (directory), FILE (file entry) - streamed sequentially |
| Compression | None at software level; relied on hardware compression of tape drives when written to physical tape |
| Encryption | Not supported - NTBackup .bkf files carry no encryption layer |
| Typical file size | Tens of MB to many GB, depending on backup scope (files-only vs. full system state) |
| Integrity checking | Per-block CRC within individual MTF descriptor blocks; no whole-file checksum, making corruption common on aged backups |
| Associated operating systems | Windows NT 4.0, Windows 2000, Windows XP, Windows Server 2003 |
| Superseded by | Windows Server Backup (VHD/VHDX-based), introduced in Windows Vista / Server 2008; NTBackup dropped from Vista onward |
| MIME type | application/octet-stream (informal: application/x-ntbackup) |
| Restore on modern Windows | Windows NT Backup - Restore Utility (ntbackup.msi, KB974674) for Vista/7; third-party tools required for Windows 8 and later |
| Developer lineage | Microsoft, based on technology licensed from Veritas/Seagate Backup Exec |
| Multi-volume support | Designed to span multiple tape volumes via VOLB descriptor blocks |
| System state backup | Can capture Windows Registry, boot files, and COM+ class registration database in addition to user files |
| Released | 1997 (NTBackup in Windows NT 4.0; widely used through Windows XP/Server 2003) |
| Latest version | MTF as used by NTBackup in Windows XP / Server 2003 (last OS to ship NTBackup) |
| Specification | en.wikipedia.org |
BKF conversions
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