7z is a compressed archive file format that supports several different data compression, encryption and pre-processing filters. The 7z format initially appeared as implemented by the 7-Zip archiver. Both the 7-Zip program and a library to read the 7z file format are publicly available under the terms of the GNU Lesser General Public License. A filename extension is a suffix to the name of a computer file applied to indicate its type. ... An Internet media type,[1] originally called a MIME type after MIME and sometimes a Content-type after the name of a header in several protocols whose value is such a type, is a two-part identifier for file formats on the Internet. ... Source coding redirects here. ... A file format is a particular way to encode information for storage in a computer file. ... Source coding redirects here. ... Encrypt redirects here. ... 7-Zip is an open source file archiver designed originally for the Microsoft Windows operating system, and later made available to other systems. ... The GNU Lesser General Public License (formerly the GNU Library General Public License) or LGPL is a free software license published by the Free Software Foundation. ...

The MIME type of 7z is application/x-7z-compressed. An Internet media type,[1] originally called a MIME type after MIME and sometimes a Content-type after the name of a header in several protocols whose value is such a type, is a two-part identifier for file formats on the Internet. ...

Features and enhancements

The 7z format provides the following main features:

• Open, modular architecture which allows any compression, conversion, or encryption method to be stacked.
• High compression ratios (depending on the compression method used)
• Strong Rijndael/AES-256 encryption.
• Large file support (up to approximately 16 exabytes).
• Unicode file names
• Support for solid compression, where multiple files of like type are compressed within a single stream, in order to exploit the combined redundancy inherent in similar files.
• Compression of archive headers.

The format's open architecture allows additional future compression methods to be added to the standard. An open format is a published specification for storing digital data, usually maintained by a non-proprietary standards organization, and free of legal restrictions on use. ... This article is about the block cipher. ... In cryptography, the Advanced Encryption Standard (AES), also known as Rijndael, is a block cipher adopted as an encryption standard by the U.S. government. ... Encrypt redirects here. ... An exabyte (derived from the SI prefix exa-) is a unit of information or computer storage equal to approximately one quintillion bytes. ... The Unicode Standard, Version 5. ... In computing, solid compression refers to a method for data compression of multiple files, wherein all the compressed files are treated as a single data block. ... In information technology, Header refers to supplemental data placed at the beginning of a block of data being stored or transmitted, which contain information for the handling of the data block. ...

Compression method filters

The following compression methods are currently defined:

• LZMA – A variation of the LZ77 algorithm, using a sliding dictionary up to 1 GB in length for duplicate string elimination. The LZ stage is followed by entropy coding using a Markov chain based range coder and Patricia trees.
• Bzip2 – The standard Burrows-Wheeler transform algorithm. Bzip2 uses two reversible transformations; BWT, then Move to front with Huffman coding for symbol reduction (the actual compression element).
• PPMD – Dmitry Shkarin's 2002 PPMdH (PPMII/cPPMII) with small changes: PPMII is an improved version of the 1984 PPM compression algorithm (prediction by partial matching).
• DEFLATE – Standard algorithm based on 32 kB LZ77 (LZSS actually) and Huffman coding. Deflate is found in several file formats including ZIP, gzip, PNG and PDF. 7-Zip contains a from-scratch DEFLATE encoder that frequently beats the defacto zlib version in compression size, but at the expense of CPU usage.

A suite of recompression tools called AdvanceCOMP contains a copy of the DEFLATE encoder from the 7-Zip implementation; these utilities can often be used to further compress the size of existing gzip, ZIP, PNG, or MNG files. LZMA, short for Lempel-Ziv-Markov chain-Algorithm, is a data compression algorithm in development since 2001 and used in the 7z format of the 7-Zip archiver. ... LZ77 and LZ78 are the names for the two lossless data compression algorithms published in papers by Abraham Lempel and Jacob Ziv in 1977 and 1978. ... An entropy encoding is a coding scheme that assigns codes to symbols so as to match code lengths with the probabilities of the symbols. ... In mathematics, a Markov chain, named after Andrey Markov, is a discrete-time stochastic process with the Markov property. ... This article needs cleanup. ... A radix tree, Patricia trie/tree, or crit bit tree is a specialized set data structure based on the trie that is used to store a set of strings. ... The correct title of this article is . ... The Burrows-Wheeler transform (BWT, also called block-sorting compression), is an algorithm used in data compression techniques such as bzip2. ... The move-to-front (or MTF) transform is an encoding of data (typically a stream of bytes) designed to improve the performance of entropy encoding techniques of compression. ... In computer science and information theory, Huffman coding is an entropy encoding algorithm used for lossless data compression. ... PPM is an adaptive statistical data compression technique based on context modeling and prediction. ... PPM is an adaptive statistical data compression technique based on context modeling and prediction. ... DEFLATE is a lossless data compression algorithm that uses a combination of the LZ77 algorithm and Huffman coding. ... LZ77 and LZ78 are the names for the two lossless data compression algorithms published in papers by Abraham Lempel and Jacob Ziv in 1977 and 1978. ... Lempel-Ziv-Storer-Szymanski (LZSS) is a lossless data compression algorithm, a derivative of LZ77, that was created in 1982 by James Storer and Thomas Szymanski. ... In computer science and information theory, Huffman coding is an entropy encoding algorithm used for lossless data compression. ... The ZIP file format is a popular data compression and archival format. ... gzip is a software application used for file compression. ... PNG (Portable Network Graphics), sometimes pronounced as ping, is a relatively new bitmap image format that is becoming popular on the World Wide Web and elsewhere. ... PDF is an abbreviation with several meanings: Portable Document Format Post-doctoral fellowship Probability density function There also is an electronic design automation company named PDF Solutions. ... zlib is an open-source, cross-platform data compression library. ... AdvanceCOMP is a set of command line data (re-)compression tools. ... gzip is a software application used for file compression. ... The ZIP file format is a popular data compression and archival format. ... PNG (Portable Network Graphics), sometimes pronounced as ping, is a relatively new bitmap image format that is becoming popular on the World Wide Web and elsewhere. ... MNG (pronounced in IPA) is a public file format for animated images. ...

Pre-processing filters (for executable files)

The LZMA SDK comes with the BCJ / BCJ2 preprocessor included, so that later stages are able to achieve greater compression: For x86, ARM, PowerPC (PPC), IA64 and ARM Thumb processors, jump targets are normalized before compression by changing relative position into absolute values. For x86, this means that near jumps, calls and conditional jumps (but not short jumps and conditional jumps) are converted from the machine language "jump 1655 bytes backwards" style notation to normalized "jump to address 5554" style notation. x86 or 80x86 is the generic name of a microprocessor architecture first developed and manufactured by Intel. ... The ARM architecture (previously, the Advanced RISC Machine, and prior to that Acorn RISC Machine) is a 32-bit RISC processor architecture developed by ARM Limited that is widely used in a number of embedded designs. ... PowerPC is a RISC microprocessor architecture created by the 1991 Apple–IBM–Motorola alliance, known as AIM. Originally intended for personal computers, PowerPC CPUs have since become popular embedded and high-performance processors as well. ... In computing, IA-64 (Instruction Architecture-64) is a 64-bit processor architecture developed in cooperation by Intel and Hewlett-Packard for processors such as Itanium and Itanium 2. ... The ARM architecture (previously, the Advanced RISC Machine, and prior to that Acorn RISC Machine) is a 32-bit RISC processor architecture developed by ARM Limited that is widely used in a number of embedded designs. ...

• BCJ - Converter for 32-bit x86 executables. Normalise target addresses of near jumps and calls from relative distances to absolute destinations.
• BCJ2 - Pre-processor for 32-bit x86 executables. BCJ2 is an improvement on BCJ, adding additional x86 jump/call instruction processing. Near jump, near call, conditional near jump targets are split out and compressed separately in another stream.

Similar executable pre-processing technology is included in other software; the RAR compressor features displacement compression for 32-bit x86 executables and IA64 Itanium executables, and the UPX runtime executable file compressor includes support for working with 16 bit values within DOS binary files. REDIRECT RAR (file format) ... UPX, the Ultimate Packer for eXecutables, is an open source executable packer (EXE packer) supporting a number of file formats. ... This article is about the family of closely related operating systems for the IBM PC compatible platform. ...

Encryption

The 7z format supports encryption with the AES algorithm with a 256-bit key. The key is generated from a user-supplied passphrase using an algorithm based on the SHA-256 hash algorithm. The SHA-256 is executed 256K times which causes a significant delay on slow PCs before compression or extraction starts. This technique is called key strengthening and is used to make a brute-force search for the passphrase more difficult. The 7z format provides the option to encrypt the filenames of a 7z archive. Encrypt redirects here. ... In cryptography, the Advanced Encryption Standard (AES), also known as Rijndael, is a block cipher adopted as an encryption standard by the U.S. government. ... A passphrase is a sequence of words or other text used to control access to a computer system, program or data. ... Sha (Ш, ш) is a letter of the Cyrillic alphabet, representing the consonant sound or . ... A hash function is a reproducible method of turning some kind of data into a (relatively) small number that may serve as a digital fingerprint of the data. ... In cryptography, key strengthening or key stretching refer to techniques used to make a weak key such as a password or passphrase stronger, i. ... In computer science, a brute-force search consists of systematically enumerating every possible solution of a problem until a solution is found, or all possible solutions have been exhausted. ...

Limitations

The 7z format does not store UNIX owner/group permissions, and hence can be inappropriate for backup/archival purposes. A workaround is to convert your data to a tar bitstream before compressing with 7z. Most modern file systems have methods of administering permissions or access rights to specific users and groups of users. ... In computing, tar (derived from tape archive) is both file format (in the form of a type of archive bitstream) and the name of the program used to handle such files. ...

7z support at present

Listed below is a guide to how currently available archiving software supports the 7z archive format. A file archiver combines a number of files together into one archive file, or a series of archive files, for easier transportation or storage. ...

Full support

These programs support both the creation of and adding files to 7z archives, not just reading files in them.

Linux

• Peazip (GPL)
• File Roller (GPL)
• Ark (GPL) (acts as a wrapper around p7zip)
• p7zip (GPL)
• Karchiver (GPL)

PeaZip is an open source OS-portable file archiver, released under LGPL for Microsoft Windows and Linux (Linux version requires libgdk_pixbuf library). ... File-roller is an archive manager for the GNOME environment. ... Ark is an archiving tool for KDE, included into kdeutils package. ... p7zip is a port of the command line version of the 7-Zip file archiver—famous for its introduction of the high-compression LZMA format—to POSIX-conforming operating systems, such as Unix, Linux, Windows NT (or greater version) and Mac OS X. It is free software, available under the...

Mac

• The Unarchiver (freeware)
• 7zX (freeware)
• BetterZip (shareware)
• EZ 7z (freeware)
• p7zip (GPL)
• Apimac Compress Files 3 (shareware)

The Unarchiver is an open source data compression utility, which supports more formats than BOMArchiveHelper, the built-in archive unpacker program in Mac OS X. It can also handle filenames in foreign character sets, created with non-English versions of other operating systems. ... 7zX is a file archiver for Mac OS X that handles the 7z archive file format. ... EZ 7z is a compression application made by Leif Heflin for Mac OSX that handles . ... p7zip is a port of the command line version of the 7-Zip file archiver—famous for its introduction of the high-compression LZMA format—to POSIX-conforming operating systems, such as Unix, Linux, Windows NT (or greater version) and Mac OS X. It is free software, available under the...

Windows

• Peazip

• 7-Zip
• Altap Salamander
• IZArc (no support for Ultra compression or Solid format)
• PowerArchiver
• QuickZip
• ShellZip
• SimplyZip
• Squeez
• TUGZip
• ZipGenius
• UltimateZip

PeaZip is an open source OS-portable file archiver, released under LGPL for Microsoft Windows and Linux (Linux version requires libgdk_pixbuf library). ... 7-Zip is an open source file archiver designed originally for the Microsoft Windows operating system, and later made available to other systems. ... This article is being considered for deletion in accordance with Wikipedias deletion policy. ... IZArc is a freeware file archiver for Microsoft Windows. ... PowerArchiver is a proprietary file archiver designed for Microsoft Windows users, developed by ConeXware Inc. ... Squeez is a shareware file archiver and data compression utility by Speedproject. ... TUGZip is a freeware file archiver for Microsoft Windows. ... ZipGenius is a freeware file archiver designed for Microsoft Windows users, developed by Matteo Riso of M.Dev Software. ...

Extract-only support

These programs support only reading files in existing 7z archives. They do not allow creating new archives, or adding more files to existing archives.

Mac

• The Unarchiver (LGPL)
• Zipeg (freeware)

The Unarchiver is an open source data compression utility, which supports more formats than BOMArchiveHelper, the built-in archive unpacker program in Mac OS X. It can also handle filenames in foreign character sets, created with non-English versions of other operating systems. ... GNU logo The GNU Lesser General Public License (formerly the GNU Library General Public License) is an FSF approved Free Software license designed as a compromise between the GNU General Public License and simple permissive licenses such as the BSD license and the MIT License. ... Zipeg is a decompression application made by Leo Kuznetsov for Mac OS X that handles zip files. ...

Windows

• Bread-Zip
• ALZip
• ExtractNow
• WinRAR (read-only support, but 7z creation will most likely be included in the future ^[1])
• Zipeg

ALZip is an archive and compression utility from ESTsoft for Microsoft Windows. ... WinRAR is a shareware file archiver and data compression utility by Eugene Roshal. ... Zipeg is a decompression application made by Leo Kuznetsov for Mac OS X that handles zip files. ...

Amiga

• XAD (with 7-Zip plug-in^[2])

The XAD system is an open source client based archiving and unarchiving system. ...

References

This article or section needs sources or references that appear in reliable, third-party publications. Primary sources and sources affiliated with the subject of the article are generally not sufficient for a Wikipedia article. Please include more appropriate citations from reliable sources, or discuss the issue on the talk page. This article has been tagged since April 2007.

1. ^ Best Archive Tool - DonationCoder.com
2. ^ Aminet - util/arc/xad_7z.lha

See also

• Comparison of archive formats
• List of archive formats
• Free file format
• Open format

Image File history File links Free_Software_Portal_Logo. ... This article or section is in need of attention from an expert on the subject. ... This is a list of file formats used by archivers and compressors. ... A free file format is a file format that is free of any patents or copyright. ... An open format is a published specification for storing digital data, usually maintained by a non-proprietary standards organization, and free of legal restrictions on use. ...

External links

• 7z Format — General description about the 7z archive format.
• 7Z File Extension
• 7zip Unix Manual and 7z format