A SIT file is a compressed archive file created with Micro StuffIt software. This is the original standard file format that was introduced by StuffIt. SIT file format is commonly used on Macintosh systems, but now it is supported on both Windows and Macintosh platforms. StuffIt extended the SIT file format to SITX which offers more compression as compared to SIT files. SIT files can be opened with Smith Micro StuffIt Deluxe Mac 16 software.
SIT File Format - More Information
SIT files are saved in binary file format and their internal file format details are not available publicly. It was introduced by the Aladdin Systems and was introduced to compress files to archives.