What is the IMA file format?
Files with the .ima extension contain disk images - raw, sector-by-sector copies of a floppy disk. An .ima file can be mounted by dedicated applications as a virtual disk that the system accesses just like a standard physical disk.
The .ima format was originally designed as the default disk image format for WinImage (released 1993). Today, .ima files are most commonly used to store 3.5-inch HD diskette images, with the standard size being exactly 1,474,560 bytes (1.44 MB). Emulators such as DOSBox, VirtualBox and QEMU also use .ima for virtual boot media.
Because the format carries no container header, it is identified by its embedded FAT12 filesystem and the 0x55AA boot-sector signature at byte offset 510. .ima is essentially interchangeable with .IMG and .VFD raw floppy images; WinImage's compressed variant uses the .IMZ extension.
Security & safety
RISK: LOWA raw .ima image is passive data with no code of its own. The real caveat is what the disk contained: old floppy images can carry DOS-era boot-sector viruses or infected executables, which are harmless sitting in a file but can matter if you boot the image in an emulator/VM or write it back to a real floppy - run a scan on extracted files and treat unknown vintage boot disks with care. Download imaging tools only from official sites (winimage.com, 7-zip.org), not repack portals.
Format details
in a nutshellPrograms that open IMA files
Windows5 apps
IsoBuster
Freemium Open the image to inspect and extract files; useful for damaged images. Free tier available. 
7-Zip
Open-source Right-click the .ima > 7-Zip > Open archive to browse and extract the files (it reads the FAT filesystem inside). 
VirtualBox
Open-source In a VM's storage settings add a floppy controller and attach the .ima as a virtual floppy disk. 
WinImage
Paid Open the .ima to view, extract, add files, or write it back to a physical floppy. The classic native tool (shareware). 
86Box / PCem
Open-source Mount the .ima in the emulated floppy drive to run vintage DOS/Windows software authentically. 
macOS2 apps
Disk Utility / hdiutil (built-in)
Built-in Many FAT .ima images mount via 'hdiutil attach disk.ima'; otherwise use a VM/emulator. 
Linux2 apps
mount (loop device, built-in)
Built-in Run: 'sudo mount -o loop disk.ima /mnt' to browse the FAT contents; unmount when done.
QEMU / DOSBox-X
Open-source Attach the .ima as a virtual floppy to run the disk's software in emulation. Technical details
deep spec| Encoding | Binary (raw byte stream) |
| Byte order | Little-endian (FAT and x86 boot-sector fields) |
| Container | Raw sector-by-sector image; no file-level wrapper or proprietary header of its own |
| Embedded filesystem | FAT12 (1.44 MB and smaller floppies); FAT16 for larger disk geometries |
| Standard file sizes | 360 KB (DD 5.25-inch), 720 KB (DD 3.5-inch), 1,474,560 bytes (HD 1.44 MB), 2,949,120 bytes (ED 2.88 MB) |
| Boot sector signature | 0x55AA at byte offset 510-511 (standard x86 boot-sector marker) |
| OEM string | 8-byte ASCII at boot-sector offset 3 (e.g. 'MSDOS5.0', 'mkfs.fat') |
| Compression | Uncompressed raw data; the separate .imz format adds zlib compression on the same image structure |
| MIME type | application/octet-stream (generic); application/x-ima (informal) |
| Root directory capacity | 224 entries on a standard 1.44 MB FAT12 image (set by BPB fields in the boot sector) |
| Disk geometry (1.44 MB) | 80 cylinders × 18 sectors/track × 2 heads × 512 bytes/sector |
| File identification | File size matching a known disk capacity plus embedded FAT signatures - no dedicated .ima magic number exists |
| Related formats | .img and .vfd share identical raw structure; most tools handle all three interchangeably |
| Emulator support | DOSBox, VirtualBox, QEMU and 86Box all accept .ima directly as a virtual floppy drive |
| Released | 1990s (DOS/Windows floppy-imaging era; WinImage 1993) |
| Latest version | No versioned spec - a raw image; WinImage still distributes/creates .ima |
| Open standard | Yes · royalty-free |
| Specification | www.winimage.com |
IMA conversions
Community Q&A
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