What is the MRIMG file format?
A .mrimg file is a proprietary disk image backup created by Macrium Reflect, a Windows disaster-recovery and bare-metal restore application developed by Paramount Software UK. The file captures a sector-level snapshot of an entire disk or individual partition, storing only used sectors inside a binary container that includes a metadata header with the source disk GUID, partition layout, creation timestamp, compression settings, and an optional AES-256 encryption flag.
Full, incremental, and differential backup types all use the .mrimg extension; incremental images reference a parent full image in a backup chain. Integrity is maintained through SHA-256 checksums on data blocks, and Reflect includes a built-in image verification function. A .mrimg image can be mounted as a virtual drive in Windows Explorer or browsed file-by-file for granular file recovery without performing a full restore.
In 2023, Macrium Reflect X introduced an incompatible successor format, .mrimgx, which replaces the LZ-based compression of Reflect 7/8 with Zstandard. Reflect X retains the ability to restore from legacy .mrimg files. Also in 2023, Macrium discontinued its free tier. Paramount Software UK was acquired by Carbonite/OpenText in 2021, and the Macrium Reflect product line continues.
Security & safety
RISK: LOWThe .mrimg container itself is not a malware vector. However, the disk image contains a complete operating system snapshot that may include malware present on the source machine at backup time. Restoring an infected image reintroduces the infection. AES-256 encrypted images are unreadable without the password. Very large files (TB-scale) can consume all available disk space if restoration destination is miscalculated.
Format details
in a nutshellPrograms that open MRIMG files
Windows2 apps
Macrium Reflect
Paid Open Macrium Reflect → Restore tab → Browse for Image → select the .mrimg file. Use 'Mount Image' to browse files or 'Restore Image' for full bare-metal recovery. 
Macrium Reflect Rescue Media (bootable WinPE)
Paid Boot from Macrium rescue USB/DVD, then Restore → select .mrimg from backup location to restore to a bare-metal or new disk. Technical details
deep spec| Backup scope | Sector-level disk or partition image; only used sectors are captured, making the image significantly smaller than a raw sector-by-sector copy |
| Encoding | Binary, little-endian; proprietary Macrium binary container format |
| Compression | LZ-based (Reflect 7/8) with configurable compression level; Reflect X uses Zstandard (zstd) for the newer .mrimgx successor format |
| Encryption | AES-256, optional; applied to backup data blocks with password protection |
| Integrity verification | SHA-256 checksums on backup data blocks; Reflect includes a built-in image-verify function for pre-restore validation |
| Backup chain types | Full, incremental, and differential backup images all use the .mrimg extension; incremental images reference a parent full image |
| Typical file size | 1 GB - 2+ TB depending on source disk/partition size and compression ratio |
| File system coverage | Captures NTFS, FAT32, and exFAT structures within data blocks; supports bare-metal restore to dissimilar hardware |
| Mount capability | Can be mounted as a virtual drive in Windows Explorer, or browsed file-by-file for individual file recovery without a full restore |
| Split archives | Image sets may span multiple .mrimg files with a sequence index, supporting FAT32 volumes and network shares with file-size limits |
| Platform | Windows only - both the backup agent and the Rescue Media (bootable WinPE) environment |
| Format succession | .mrimgx (Reflect X, 2023) replaces .mrimg for new backups using Zstandard compression; Reflect X can restore legacy .mrimg files, but Reflect 8 cannot read .mrimgx |
| Bootable recovery | Macrium Rescue Media (bootable WinPE) can restore .mrimg images to bare metal without a running Windows installation |
| Released | Mid-2000s with early Macrium Reflect; product launched 2006 |
| Latest version | Macrium Reflect 8 (.mrimg); superseded by .mrimgx in Reflect X (2023) |
| Specification | knowledgebase.macrium.com |
MRIMG conversions
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