ARC (compression format)

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File Format
Name ARC (compression format)
Extension(s) .arc, .ark
Released 1985

ARC was for a time (1985-89) the leading file archiving and file compression format in the BBS world, replacing the formats used by earlier utilities which generally only did one of the two functions (either combining multiple files in one file for convenient download, or shortening the file length to take less download time and disk space). Combining the two functions in one utility simplified the process of preparing files for download and extracting them at the other end, leading to a rapid rise in popularity for the utility (also called ARC) and format both.

However, the ARC format suffered an equally rapid decline in its popularity after the company that published the ARC utility (called System Enhancement Associates or SEA, run by Thom Henderson who was very active in FidoNet) brought a successful trademark and copyright suit against rival Phil Katz, whose PKARC and PKXARC utilities were compatible with the ARC file format. The lawsuit was widely regarded by the BBS community as being a "David vs. Goliath" case of a faceless corporation bullying a "little guy", though in fact both companies were small, home-based operations. Nevertheless, the fallout from the suit led to rapid adoption of the competing ZIP format, introduced by Katz in 1989, and ARC files are no longer commonly encountered.

The fact that archives from an early period of BBSing are often in this format encourages bad puns referring to those who trawl such old archives as "Raiders of the lost ARC."

There are, unfortunately, also several other incompatible file formats that have been used over the years with an "ARC" designation or file extension, so it's possible that a data set that is purportedly of type "ARC" is not actually of this format. Others include the FreeArc format and the Internet Archive ARC format.


  • File extension: .ARC (or conventionally .ARK on CP/M)
  • MIME type (Internet media type): Has no specific registered type; generic binary application/octet-stream is generally used, or perhaps unregistered custom types with an x- prefix
  • Uniform Type Identifier (Apple): public.archive.arc

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