Stuffit

StuffIt is a software utility for archiving and compressing files for the Apple Macintosh and is still the most popular program for Mac-related downloads. It was written by Raymond Lau in the 1980s when he was a high school student in New York City and further developed by Aladdin Systems, Inc.. StuffIt is shareware and may be freely distributed, but it is not "Free" in the Open Source sense.

StuffIt-compressed files, typically, possess the filename extension .sit .

StuffIt is also available for Microsoft Windows and Linux.

StuffIt Expander is a free program for expanding compressed files.