7-Zip is a file archiver with a high compression ratio. With these tools you can easily send large quantities of information or open compressed files you receive without hassle. 7-Zip is open source software. Most of the source code is under the GNU LGPL license. The unRAR code is under a mixed license: GNU LGPL + unRAR restrictions. You can use 7-Zip on any computer, including a computer in a commercial organization. You don’t need to register or pay for 7-Zip

Compression ratio results are very dependent upon the data used for the tests. Usually, 7-Zip compresses to 7z format 30-70% better than to zip format. And 7-Zip compresses to zip format 2-10% better than most of other zip compatible programs.

The Main Features of 7-Zip:

High compression ratio in 7z format with LZMA and LZMA2 compression.
Supported packing / unpacking: 7z, XZ, BZIP2, GZIP, TAR, ZIP and WIM
Supported unpacking: ARJ, CAB, CHM, CPIO, CramFS, DEB, DMG, FAT, HFS, ISO, LZH, LZMA, MBR, MSI, NSIS, NTFS, RAR, RPM, SquashFS, UDF, VHD, WIM, XAR and Z.
For ZIP and GZIP formats, 7-Zip provides a compression ratio that is 2-10 % better than the ratio provided by PKZip and WinZip.
Strong AES-256 encryption in 7z and ZIP formats.
Self-extracting capability for 7z format.
Integration with Windows Shell.
Powerful File Manager.
Powerful command line version.
Plugin for FAR Manager.
Localizations for 87 languages.