From Just Solve the File Format Problem
Revision as of 16:04, 10 May 2024 by Jsummers (Talk | contribs)

(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)
Jump to: navigation, search
File Format
Name StuffIt
Extension(s) .sit
MIME Type(s) application/x-stuffit, application/x-sit
PRONOM fmt/639, fmt/1459, fmt/1460
Type Code SIT!
Wikidata ID Q59535034
Released 1987

If somebody tells you StuffIt, they might be brushing you off rudely, but, especially if they're a Mac user, they might just be recommending their favorite file archiver. Since the late 1980s, StuffIt has been the most popular file archiving system for the Mac platform, with a version available for Windows as well (though it never achieved a high degree of popularity there). Like a number of other Mac archivers, StuffIt supports storing the Resource Fork along with the "regular" file, which is one reason Mac-specific archivers were popular in preference to "generic" ones like ZIP. StuffIt also produced more compact archives than its main competitor PackIt at the time it was first released in 1987, when its author, Raymond Lau, was still in high school. It has faced other competitors since, but remained on top. In recent times, however, with OS X being Unix-based, traditional Unix archiving and compression programs such as tar and gzip are getting increasing use on Macs.

The makers of StuffIt have also released the newer format StuffIt X.

These formats remain proprietary, and do not interoperate with other programs unless they are officially licensed.



StuffIt versions through 1.5.1 are credited to Raymond Lau. Following versions are by Aladdin Systems. Aladdin Systems was acquired by IMSI in 2004, and renamed to Allume Systems shortly afterward. In 2005, Allume Systems was acquired by Smith Micro.

Compression methods

ID Name Description
0 None Uncompressed
2 LZW LZW, similar to compress (Unix)
3 Huffman Static Huffman coding. Same compression as PackIt.
5 LZAH LZ77+Huffman with Adaptive Huffman coding. Similar or identical to LHA's "lh1" method.
6 Fixed Huffman Segmented. PackBits, then optional Huffman coding. The set of Huffman codes is predefined, but the meaning of a code can be different in each segment.
8 MW "Miller-Wegman". Presumably LZMW.
13 LZ+Huffman
14 Installer
15 Arsenic

See also


  • Older StuffIt archives begin with ASCII "SIT!", and have "rLau" at offset 10. The byte at offset 14 (the version number) is 0x01 for versions 1.5.x and earlier, or 0x02 for versions 1.6 - 4.5.
  • StuffIt 5 archives begin with a string of text that always starts with "StuffIt (c)1997". The byte at offset 82 has value 0x05.

Some .SIT files start with a 128-byte MacBinary header.


Format info

Original format:

V5 format:

Other information:



Sample files

Other links

Personal tools