0 7-Zip

7-Zip is a file archiver with a high compression ratio.
Download 7-Zip 9.20 (2010-11-18) for Windows:

Link	Type	Windows	Size
Download	.exe	32-bit x86	1 MB
Download	.msi	64-bit x64	1 MB

The download links above redirect you to download pages on SourceForge.net

License

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. Check license information here: 7-Zip license.
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.

The main features of 7-Zip

• High compression ratio in 7z format with LZMA and LZMA2 compression
• Supported formats:
  • Packing / unpacking: 7z, XZ, BZIP2, GZIP, TAR, ZIP and WIM
  • Unpacking only: 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 79 languages

7-Zip works in Windows 7 / Vista / XP / 2008 / 2003 / 2000 / NT / ME / 98. There is a port of the command line version to Linux/Unix.
On 7-Zip's Source Forge Page you can find a forum, bug reports, and feature request systems.

Compression ratio

We compared 7-Zip with some of the leading archivers.
FILE SETS: Mozilla Firefox 1.0.7 for Windows and Google Earth 3.0.0616 for Windows after full installation.

Archiver	Mozilla Firefox		Google Earth
	161 files 15,684,168 bytes		115 files 23,530,652 bytes
	Compressed size	Ratio	Compressed size	Ratio
7-Zip 4.23 (7z format)	4621135	100%	6109183	100%
WinRAR 3.50	5021556	109%	6824892	112%
CABARC 5.1	5131393	111%	7434325	122%
WinZip 10.0 beta (maximum-PPMd)	5277118	114%	8200708	134%
7-Zip 4.23 (zip format)	6222627	135%	8909446	146%
WinZip 10.0 beta (maximum-portable)	6448666	140%	9153898	150%

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.