What is the ARK file format?
An .ark file is a compressed archive that uses the same binary format as SEA ARC (System Enhancement Associates' ARC archiver), with the .ark extension adopted by convention on CP/M BBS systems during the mid-1980s to distinguish CP/M software packages from DOS-targeted .arc archives.
The format is identical to ARC at the binary level: each member file is introduced by the byte 0x1A (Control-Z), followed by a compression-method byte, a fixed header containing the filename, uncompressed and compressed sizes, a modification date, and a 16-bit CRC. The archive closes with the sequence 0x1A 0x00. Supported compression methods include stored (no compression), packed, squeezed, and multiple crunched variants - the same set ARC supports.
Today .ark files appear only in retro-computing contexts: old CP/M software collections, vintage BBS archives, and digital preservation projects. Modern archivers including PeaZip and IZArc can extract them. The format was rendered obsolete by ZIP in 1989, which introduced better compression ratios and a central directory enabling random-access lookups.
Because there is no central directory, extracting a single file requires a sequential scan of the entire archive from the beginning.
Security & safety
RISK: LOWThe ARK/ARC format is inert data. Like any archive, it can contain executables or scripts, so scan the extracted contents before running anything from an untrusted source. For CP/M era software, executables are CP/M binaries that won't run on modern OS without an emulator (e.g. QEMU or RunCPM). Download archivers only from official sites (PeaZip, IZArc).
Format details
in a nutshell- QuArk game archive - QuArk (Quake Army Knife) map editor uses .ark for some Quake-engine game archives; a completely different proprietary format.
- Various game engine data archive - Multiple games use .ark for proprietary asset containers (e.g. Valve/Source, Guitar Hero) - unrelated to the CP/M archive format.
Programs that open ARK files
Windows3 apps
PowerDesk Pro
Paid File manager that may handle .ark via archiver shell extensions. Less reliable than PeaZip/IZArc for legacy ARC format - use PeaZip/IZArc instead. 
PeaZip
Open-source Right-click the .ark > PeaZip > Extract. Has the broadest legacy-ARC/ARK support of mainstream Windows archivers. 
macOS1 app
The Unarchiver
Free Double-click the .ark; The Unarchiver supports many legacy formats including ARC. Free on Mac App Store. 
Linux2 apps
Technical details
deep spec| Binary format | Identical to SEA ARC format at the binary level; same member structure and magic bytes |
| Magic bytes | `0x1A` (Control-Z) at start of each member; `0x1A 0x00` = end-of-archive marker |
| Byte order | Little-endian |
| Per-member header | Filename, uncompressed size, compressed size, modification date, 16-bit CRC |
| Compression methods | Stored (0x01), packed (0x02), squeezed (0x03), crunched (0x04-0x06), squashed (0x08), crushed (0x09) |
| Integrity check | 16-bit CRC per member file, stored in the per-file header |
| Archive structure | Sequential only - no central directory; locating a file requires scanning from the beginning |
| Naming convention | `.ark` used on CP/M BBS systems to distinguish CP/M packages from DOS `.arc` archives |
| Typical file size | 10 KB - 5 MB (typical CP/M software distribution size) |
| Platform origin | CP/M; later accessible via MS-DOS ARC-compatible tools |
| Obsolescence | Superseded by ZIP (1989); encountered today only in retro-computing and digital preservation |
| Released | Circa 1985-1986 (alongside SEA ARC; .ark convention used on CP/M BBS systems) |
| Latest version | No versioning beyond the ARC format versions; format is obsolete |
| Open standard | Yes · royalty-free |
| Specification | fileformats.archiveteam.org |
ARK conversions
Community Q&A
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