7-Zip is a free and open source file archiver. 7-Zip operates with the 7z archive format, but can read and write several other archive formats. The program can be used from a command line interface, graphical user interface, or with a window-based shell integration. 7-Zip began in 1999[1] and is actively developed by Igor Pavlov. The cross-platform version of the command line utility, p7zip, is also available.[4]
7-Zip is free software distributed under the GNU Lesser General Public License (LGPL). It was the winner of the SourceForge.net 2007 community choice awards for "Technical Design" and for "Best Project".[
The 7z archive format
By default, 7-Zip creates 7z format archives with a .7z file extension. Each archive can contain multiple directories and files. As a container format, security or size reduction are achieved using a stacked combination of filters. These can consist of pre-processors, compression algorithms, and encryption filters.
The core .7z compression uses a variety of algorithms, the most common of which are bzip2, LZMA2, and LZMA. Developed by Igor Pavlov, LZMA is a relatively new system, making its debut as part of the 7z format. LZMA consists of a large LZ-based sliding dictionary up to 4 GB in size, backed by a range coder.[6]
The native 7z file format is open and modular. All filenames are stored as Unicode.[7]
The official 7z file format specification is distributed with the program's source code. The specification can be found in plain text format in the 'doc' subdirectory of the source code distribution.
Other supported formats
7-Zip supports a number of other compression and non-compression archive formats (both for packing and unpacking) including 7z, ZIP, GZip, bzip2, xz, tar and WIM. The utility also supports unpacking APM, ARJ, CHM, cpio, DEB, FLV, JAR, LHA/LZH, LZMA, MSLZ, onepkg, RAR, RPM, smzip, SWF, XAR and Z archives and CramFS, DMG, FAT, HFS, ISO, MBR, NTFS, SquashFS, UDF and VHD disk images.
7-Zip is able to open some MSI files, allowing access to the meta-files within along with the main contents. Some Microsoft CAB (LZX compression) and NSIS (LZMA) installer formats can be opened. Similarly, some Microsoft executable programs (.EXEs) which are self-extracting archives or otherwise contain archived content (e.g., some setup files) may be opened as archives.
When compressing ZIP or gzip files, 7-Zip uses its own DEFLATE encoder, which is often able to achieve higher compression levels, but at lower speed, than the more common DEFLATE implementation of zlib. The 7-Zip deflate encoder implementation is available separately as part of the AdvanceCOMP suite of tools.
The decompression engine for RAR archives was developed using source code of the unRAR program.
Variants
Two command line versions are provided: 7z.exe, using external libraries; and a standalone executable 7za.exe containing built-in modules. However, 7za's compression/decompression support is limited to 7z, ZIP, gzip, bzip2, Z and tar formats. A 64-bit version is available, with support for large memory maps leading to faster compression. All versions support multi-threading.
The 7za.exe version of 7-Zip is available for Unix-like operating systems (including Linux, FreeBSD and Mac OS X), FreeDOS, OpenVMS and AmigaOS 4 under the name p7zip. It was developed and is maintained by the developer of 7-Zip for Windows – Igor Pavlov.
Features
7-Zip supports:
The 256-bit AES cipher. Encryption can be enabled for both files and the 7z directory structure. When the directory structure is encrypted, users are required to supply a password to see the filenames contained within the archive. WinZip-developed zip file AES encryption standard is also available in 7-Zip to encrypt ZIP archives with AES 256-bit, but it does not offer filename encryption as in 7z archives.[9]
Volumes of dynamically variable sizes, allowing use for backups on removable media such as writable CDs and DVDs.
Usability as a basic orthodox file manager when used in 2-panel mode.
Multiple-core CPU threading settings can be configured.
The ability to attempt to open EXE files as archives, allowing the decompression of data from inside many "Setup" or "Installer" or "Extract" type programs without having to launch them.
The ability to unpack archives with corrupted filenames, renaming the files as required.
The ability to create self-extracting single- (but not multi-) volume archives.
Command-line interface.
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