.sit

Low risk

StuffIt archive

Aladdin Systems' (now Smith Micro) 1987 archive format for classic Mac. The de-facto standard for Mac software distribution before OS X, and still occasionally encountered when digging through legacy Mac media.

MIME types

application/x-stuffit

Category

archive

Aliases

.sitx

What opens this file

The Unarchiver
StuffIt Expander
Keka

How to open by OS

Windows

StuffIt Expander for Windows, legacy unstuff.

Mac

The Unarchiver (recommended), StuffIt Expander.

Linux

`unar` via libarchive.

Ios

iZip (compatible build).

Android

ZArchiver (compatible build).

Safety notes

Older StuffIt Expander releases have multiple RCE-class CVEs. Prefer The Unarchiver today.
Files pulled from aged floppies and CD-Rs often have header corruption — handle as binary data.

Common mistakes

Some StuffIt apps haven't been ported past the 32-bit transition on macOS Catalina. The Unarchiver sidesteps this.
.sit and .sitx feel interchangeable, but StuffIt X archives can fail to open in older tooling.

Related extensions

References