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As one of the leading compression tools 7-Zip runs on million PCs. It is free to use and provides support for a lot of different file formats including .rar, .zip, .tar, .gzip and much more. It also comes with it's own format named .7z.
7-Zip is available for Windows and Windows Phone only.
SpecsUpdate
Pros
Pro Free and open source
7-Zip is free software. You can use it on any computer. You don't need to register or pay for 7-Zip (including for commercial use). 7-Zip is licensed under GNU LGPL, and the *.7z format has support across all major operating systems. There should be no trouble opening the archives under any operating system, and no need to deal with messages bugging you to register or pay for the app. Source code can be found here.
Pro Highest compression rate with LZMA2
The own file format .7z shipped with 7-Zip is one of the best formats for compressing archives.