What is the NTFS file format?
The .ntfs extension identifies a binary image of an NTFS-formatted disk partition, most commonly produced by the ntfsclone tool from the NTFS-3G project (maintained by Tuxera). Unlike a raw sector-by-sector dump, ntfsclone's "special image" format skips unallocated clusters, producing a file significantly smaller than the full partition size while still enabling exact restoration.
The special image format opens with a header containing the cluster size, total volume size, MFT record count, and a used-cluster bitmap. Only allocated NTFS clusters are stored in sequence. This makes the format efficient for backup but means the file cannot be loop-mounted directly - ntfsclone --restore-image is required to convert it back to a raw image before mounting.
The .ntfs extension itself is not standardised. Many tools use .img for the same content; .ntfs is applied by convention to explicitly identify the partition file system type and avoid confusion with FAT or ext4 images. The ntfsclone2vhd utility can convert special images to dynamic VHD format for use with Windows Disk Management or Hyper-V.
The NTFS file system was introduced with Windows NT 3.1 in 1993. The ntfsclone tool emerged in the early 2000s as part of the ntfsprogs suite, later absorbed into the NTFS-3G project.
Security & safety
RISK: MEDIUMNTFS partition images contain a complete copy of a Windows filesystem including user files, system files, and potentially credentials/sensitive data. Handle with the same care as the original disk. Restoring an image to the wrong partition will destroy existing data. Files extracted from untrusted images may contain malware.
Format details
in a nutshell- Generic raw NTFS partition dump (dd output) - A raw sector-by-sector copy of an NTFS partition (e.g., from dd if=/dev/sda1 of=out.ntfs) may get the .ntfs extension; has NTFS boot sector magic at offset 0, not ntfsclone header.
Programs that open NTFS files
Windows2 apps
7-Zip
Open-source 7-Zip can open raw NTFS partition images (not ntfsclone special format) - open as archive to browse files. Limited support; results vary. 
ntfsclone2vhd
Open-source Run ntfsclone2vhd.exe image.ntfs image.vhd - converts ntfsclone special image to VHD. Then mount the VHD in Windows Disk Management. 
Linux2 apps
ntfsclone (ntfs-3g)
Open-source ntfsclone --restore-image --overwrite /dev/sdXN image.ntfs - restores to target partition. Or: ntfsclone -O image.img --restore-image image.ntfs to convert to raw, then mount with losetup.
libguestfs / guestmount
Open-source guestmount -a image.ntfs -m /dev/sda1 /mnt/point - mounts raw NTFS images for file browsing. Technical details
deep spec| Image type | ntfsclone special image (used clusters only) or raw sector-by-sector dump |
| Special image magic | Little-endian 64-bit value 0x0D at offset 0 (ntfsclone special format header) |
| Raw NTFS boot sector | EB 52 90 + "NTFS " OEM ID at offset 3 (raw/dd-style images) |
| Header fields | Cluster size, volume size, MFT record count, device type, used-cluster count |
| Unused cluster handling | Skipped entirely in special format - reduces file size significantly vs full raw image |
| Format version | ntfsclone special image v10 (version field stored in header) |
| Compression | None natively; commonly gzip-wrapped (ntfsclone -O image.ntfs.gz --save-image) |
| Byte order | Little-endian |
| Restore requirement | ntfsclone --restore-image required - not directly loop-mountable without prior conversion |
| VHD conversion | ntfsclone2vhd converts special images to dynamic VHD for Hyper-V / Windows Disk Management |
| Platform | Created on Linux; target filesystem is Windows NTFS |
| Typical size | 500 MB - 500 GB (much smaller than partition size for special format due to skipped free clusters) |
| Extension note | Not standardised - .img equally common; .ntfs applied by convention for NTFS-specific identification |
| Released | early 2000s (ntfsclone tool; NTFS file system 1993) |
| Latest version | ntfs-3g / ntfsclone 2022.10.3 |
| Specification | manpages.ubuntu.com |
NTFS conversions
Community Q&A
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