Most people on the Mac use Stuffit Expander to compress and decompress files but there are some occasions where this either doesn't produce the best results or is not suitable for your compression needs.
7zX is a 100% free file archiver with a very high compression ratio. The developers claim that 7zX usually compresses to the unique 7z format 30-70% better than ZIP format and 2-10% better than most of other ZIP compatible programs. 7zX is highly flexible as it currently supports TAR, ZIP, GZIP, BZIP2, UNIX compress, 7z, S7z and several kinds of segmented archives. Once you've copied the program file to your application folder, simply drag files into the 7zX icon and your files will be compressed. You're asked to define exactly what level of compression you'd like to use and offered the chance to password protect your files. You'll see a brief Terminal dialog to show you the status of the compression before it's completed.
Note however that the amount of compression you get will depend on the data used for the tests. For example, DMG files will compress differently to PNG or JPG files. The good thing is that all metadata in your files, such as Spotlight metadata, is retained once the file is decompressed. The other handy thing is that 7z files will decompress even on Macs that don't have 7zX installed which makes it handy for sending to your friends.
Free to use, flexible and powerful, 7zX is a powerful alternative to zipped files or those decompressed with Stuffit Expander.
