.SITX File Extension

The .SITX file extension denotes a StuffIt X Archive file.

Key Information about .SITX Files

  • File Type: Compressed Archive (similar to a .zip or .rar file).
  • Developer: Smith Micro Software (originally Aladdin Systems).
  • Purpose: The StuffIt X format was introduced with StuffIt 7.0 (around 2002) as an evolution of the older .SIT (StuffIt) format. It was designed to offer better compression, support for long filenames, error correction, and strong encryption (512-bit RC4). It was particularly popular in the Macintosh community for safely archiving files, as it preserved Mac-specific file data like “resource forks.”

How to Open a .SITX File

To open (or “expand”) a .SITX file, you typically need a compatible file compression/archiving program.

  • StuffIt Expander: This is the dedicated, free decompression utility from Smith Micro Software, available for both macOS and Windows, and is the primary tool for opening .SITX files.
  • The Unarchiver: This is a popular, free utility for macOS that is often recommended and supports a very wide array of file formats, including .SITX (though sometimes with limitations on the more advanced features like encryption).
  • Other Archivers: Due to the proprietary nature of the format and the decline in its popularity over the years, fewer third-party archivers support the .SITX format compared to more common formats like ZIP.