RAR (file format)
Encyclopedia
RAR stands for Roshal ARchive. It is a proprietary archive file format that supports data compression
, error recovery, and file spanning
. It was developed by a Russian software engineer, Eugene Roshal
(the first letter of his surname contributing to the name of the archive format), and is currently licensed by win.rar GmbH.
The filename extension
used by RAR is
Version 1 and 2 archive files were often used in conjunction with a parchive
file archiver
to create parity file
s for error recovery when using less-than-perfect file transmission and storage media such as newsgroups, satellite transmission, and optical disc
s. Version 3 has eliminated the need for third party post-processing.
. Version 3 of RAR is based on Lempel-Ziv
(LZSS
) and prediction by partial matching (PPM) compression, specifically the PPMd implementation of PPMII by Dmitry Shkarin.
, RAR, and software that has permission from the licensor Alexander Roshal (Eugene's brother). RAR for Pocket PC is the only freeware
for creating RAR files.
Third-party programs that can only read (unpack) RAR files include: WinZip
(Windows), RarZilla (Windows), 7-Zip
(multiplatform), IZArc
(Windows), PeaZip
(Windows, Linux), Zipeg
(Windows, Mac OS X), ALZip
(Windows) and PowerArchiver
(Windows), along with the free
version of unrar
(which is available for Linux and FreeBSD). Mac OS X
readers include StuffIt Expander
, The Unarchiver
, UnRarX, and Zipeg
. Stuffit Expander is also available for Mac OS Classic with RAR support for this platform.
is commercial software (or 40-day trial) available for Microsoft Windows
. It is the only graphical tool that can write modern RAR files (RAR version 3). WinRAR's command line equivalent, RAR, is also commercial software (or 40-day trial), available for Windows, Linux
, Mac OS X
, MS-DOS
, OS/2
, and FreeBSD
. Additionally, the unrar
tool from the same distributor can be used on the aforementioned platforms to extract RAR files but not to write them.
Roshal created the RAR file format and developed programs for packing and unpacking RAR files, originally for DOS
in 1993, which were later ported
to other platforms
. The main Windows
version of the archiver
, known as WinRAR
, is distributed as trialware, requiring payment after 40 days (although it can still be used after this period, albeit with nags); shareware
versions of this program are also available for GNU/Linux, Mac OS X
, DOS
, OS/2
, and FreeBSD
, though they are all called simply "RAR".
RARLAB distributes the source code and binaries for a freeware command-line "unrar" program, although it is not under a free software
license. This program can only decompress/extract, not create RAR files.
(DLL) that can be downloaded from the official WinRAR site. It is found under "Extras".
but with a moderately better rate of compression.
7z
's LZMA
algorithm reaches a higher compression ratio than RAR, except for "multimedia" files like .wav and .bmp files where RAR uses specialized routines that outperform LZMA. Other free compression software such as NanoZip and FreeArc
usually outperform WinRAR.
Optional creation of "recovery volumes" (.rev files) with redundancy data which can be used to reconstruct missing files in a volume set.
Data compression
In computer science and information theory, data compression, source coding or bit-rate reduction is the process of encoding information using fewer bits than the original representation would use....
, error recovery, and file spanning
File spanning
File Spanning is a term used to describe the ability to package a single file or data stream into separate files of a specified size. It also implies the ability to re-combine the package files back into the original file or data stream....
. It was developed by a Russian software engineer, Eugene Roshal
Eugene Roshal
Eugene Roshal is a Russian software engineer best known as developer of:* FAR file manager * RAR file format * WinRAR file archiver...
(the first letter of his surname contributing to the name of the archive format), and is currently licensed by win.rar GmbH.
The filename extension
Filename extension
A filename extension is a suffix to the name of a computer file applied to indicate the encoding of its contents or usage....
used by RAR is
.rar for the data volume set and .rev for the recovery volume set. In previous versions, if a RAR-archive was split into many smaller files (a "multi-volume archive"), the smaller files used the extensions .rar, .r00, .r01, .r02 etc.Version 1 and 2 archive files were often used in conjunction with a parchive
Parchive
Parchive is an open source software project that emerged in 2001 to develop a parity file format, as conceived by Tobias Rieper and Stefan Wehlus...
file archiver
File archiver
A file archiver is a computer program that combines a number of files together into one archive file, or a series of archive files, for easier transportation or storage...
to create parity file
Parity file
Parity files are files that are created to accompany data files, and are used to preserve data integrity and assist in data recovery. They are useful when data files are transmitted or stored on less-than-perfect media such as newsgroup messages, satellite transmission, or optical disk...
s for error recovery when using less-than-perfect file transmission and storage media such as newsgroups, satellite transmission, and optical disc
Optical disc
In computing and optical disc recording technologies, an optical disc is a flat, usually circular disc which encodes binary data in the form of pits and lands on a special material on one of its flat surfaces...
s. Version 3 has eliminated the need for third party post-processing.
Compression algorithm
The RAR compression utility is proprietary, with a closed algorithm. RAR is owned by Alexander L. Roshal, the elder brother of Eugene RoshalEugene Roshal
Eugene Roshal is a Russian software engineer best known as developer of:* FAR file manager * RAR file format * WinRAR file archiver...
. Version 3 of RAR is based on Lempel-Ziv
LZ77 and LZ78
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. They are also known as LZ1 and LZ2 respectively. These two algorithms form the basis for most of the LZ variations including LZW, LZSS, LZMA and...
(LZSS
LZSS
Lempel-Ziv-Storer-Szymanski is a lossless data compression algorithm, a derivative of LZ77, that was created in 1982 by James Storer and Thomas Szymanski. LZSS was described in article "Data compression via textual substitution" published in Journal of the ACM .LZSS is a dictionary encoding...
) and prediction by partial matching (PPM) compression, specifically the PPMd implementation of PPMII by Dmitry Shkarin.
Versions
Several versions of the RAR format have been noted by third party developers:- RAR1.3 (original, doesn't have Rar! signature)
- RAR1.5
- RAR2
- RAR3 (current) - implemented by developers of Rarlab WinRAR version 2.9 and released in WinRAR version 3.00. Many changes including:
- File extensions changed from {volume name}.rar, {volume name}.r00, {volume name}.r01, etc. to {volume name}.part001.rar, {volume name}.part002.rar, etc.
- Encryption algorithmAlgorithmIn mathematics and computer science, an algorithm is an effective method expressed as a finite list of well-defined instructions for calculating a function. Algorithms are used for calculation, data processing, and automated reasoning...
is changed to AESAdvanced Encryption StandardAdvanced Encryption Standard is a specification for the encryption of electronic data. It has been adopted by the U.S. government and is now used worldwide. It supersedes DES...
(Advanced Encryption Standard) with 128 bit key length. - Encryption of both file data and file headers.
- Improved compression algorithm using 4MB dictionary size, Dmitry Shkarin's PPMII algorithm for file data, and selective preprocessing algorithms based on platform and source file type.
- Optional creation of "recovery volumes" (.rev files) with redundancy data which can be used to reconstruct missing files in a volume set.
- Support for archive files larger than 9 GB.
- Support for Unicode names.
Software
RAR files may be created only with commercial software WinRARWinRAR
WinRAR is a shareware file archiver and data compression utility developed by Eugene Roshal, and first released in autumn of 1993. It is one of the few applications that is able to create RAR archives natively, because the encoding method is held to be proprietary.-Developer:The current developer...
, RAR, and software that has permission from the licensor Alexander Roshal (Eugene's brother). RAR for Pocket PC is the only freeware
Freeware
Freeware is computer software that is available for use at no cost or for an optional fee, but usually with one or more restricted usage rights. Freeware is in contrast to commercial software, which is typically sold for profit, but might be distributed for a business or commercial purpose in the...
for creating RAR files.
Third-party programs that can only read (unpack) RAR files include: WinZip
WinZip
WinZip is a proprietary file archiver and compressor for Microsoft Windows and Mac OS X, developed by WinZip Computing...
(Windows), RarZilla (Windows), 7-Zip
7-Zip
7-Zip is an 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 Microsoft Windows shell integration. 7-Zip began in 1999 and is actively...
(multiplatform), IZArc
IZArc
IZArc is a proprietary file archiver for Microsoft Windows developed by Bulgarian programmer Ivan Zahariev. The program is freeware and closed source. In addition to the most commonly used archive formats, like zip, rar, gzip, tar.gz, bzip2, and 7z, IZArc handles a large number of less common formats...
(Windows), PeaZip
PeaZip
PeaZip is a file manager and file archiver for Microsoft Windows and GNU/Linux. It supports its native PEA archive format and other mainstream formats, with special focus on handling open formats...
(Windows, Linux), Zipeg
Zipeg
Zipeg is an open source free software that extracts files from ZIP, RAR and other archives. Zipeg works under Mac OS X and Windows. It is best known for its file preview ability. It is incapable of compressing files, although it is able to extract compressed ones; it supports RAR, ZIP and other...
(Windows, Mac OS X), ALZip
ALZip
ALZip is an archive and compression utility from ESTsoft for Microsoft Windows.- History :Originally ALZip was developed in 1999 as an internal application at the South Korean software company ESTsoft in response to employee frustration with using the English interface in WinZip.The Korean...
(Windows) and PowerArchiver
PowerArchiver
PowerArchiver is a proprietary file archiver for Microsoft Windows, developed by ConeXware Inc. It supports full read-write access to several different archive formats, including ZIP, 7z and Tar. Additionally, read-only support includes RAR, ACE and various disk image formats. The evaluation...
(Windows), along with the free
Free software
Free software, software libre or libre software is software that can be used, studied, and modified without restriction, and which can be copied and redistributed in modified or unmodified form either without restriction, or with restrictions that only ensure that further recipients can also do...
version of unrar
Unrar
Unrar is the name of two different command-line applications for extracting RAR archives.-RARLAB UnRAR:This version of UnRAR is distributed by RARLAB, the makers of the commercial WinRAR archivers...
(which is available for Linux and FreeBSD). Mac OS X
Mac OS X
Mac OS X is a series of Unix-based operating systems and graphical user interfaces developed, marketed, and sold by Apple Inc. Since 2002, has been included with all new Macintosh computer systems...
readers include StuffIt Expander
StuffIt Expander
StuffIt Expander is a proprietary, freeware, closed source, decompression software utility developed by Allume Systems . It runs in Mac OS Classic, Mac OS X, Microsoft Windows, and Linux x86/UNIX.As of November 2010, the latest Macintosh version is 2011 , which requires Mac OS X v10.5 or later...
, The Unarchiver
The Unarchiver
The Unarchiver is a free data decompression frontend of libxad, which supports more formats than Archive Utility , 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. The latest...
, UnRarX, and Zipeg
Zipeg
Zipeg is an open source free software that extracts files from ZIP, RAR and other archives. Zipeg works under Mac OS X and Windows. It is best known for its file preview ability. It is incapable of compressing files, although it is able to extract compressed ones; it supports RAR, ZIP and other...
. Stuffit Expander is also available for Mac OS Classic with RAR support for this platform.
WinRAR
WinRARWinRAR
WinRAR is a shareware file archiver and data compression utility developed by Eugene Roshal, and first released in autumn of 1993. It is one of the few applications that is able to create RAR archives natively, because the encoding method is held to be proprietary.-Developer:The current developer...
is commercial software (or 40-day trial) available for Microsoft Windows
Microsoft Windows
Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
. It is the only graphical tool that can write modern RAR files (RAR version 3). WinRAR's command line equivalent, RAR, is also commercial software (or 40-day trial), available for Windows, Linux
Linux
Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...
, Mac OS X
Mac OS X
Mac OS X is a series of Unix-based operating systems and graphical user interfaces developed, marketed, and sold by Apple Inc. Since 2002, has been included with all new Macintosh computer systems...
, MS-DOS
MS-DOS
MS-DOS is an operating system for x86-based personal computers. It was the most commonly used member of the DOS family of operating systems, and was the main operating system for IBM PC compatible personal computers during the 1980s to the mid 1990s, until it was gradually superseded by operating...
, OS/2
OS/2
OS/2 is a computer operating system, initially created by Microsoft and IBM, then later developed by IBM exclusively. The name stands for "Operating System/2," because it was introduced as part of the same generation change release as IBM's "Personal System/2 " line of second-generation personal...
, and FreeBSD
FreeBSD
FreeBSD is a free Unix-like operating system descended from AT&T UNIX via BSD UNIX. Although for legal reasons FreeBSD cannot be called “UNIX”, as the direct descendant of BSD UNIX , FreeBSD’s internals and system APIs are UNIX-compliant...
. Additionally, the unrar
Unrar
Unrar is the name of two different command-line applications for extracting RAR archives.-RARLAB UnRAR:This version of UnRAR is distributed by RARLAB, the makers of the commercial WinRAR archivers...
tool from the same distributor can be used on the aforementioned platforms to extract RAR files but not to write them.
Roshal created the RAR file format and developed programs for packing and unpacking RAR files, originally for DOS
DOS
DOS, short for "Disk Operating System", is an acronym for several closely related operating systems that dominated the IBM PC compatible market between 1981 and 1995, or until about 2000 if one includes the partially DOS-based Microsoft Windows versions 95, 98, and Millennium Edition.Related...
in 1993, which were later ported
Porting
In computer science, porting is the process of adapting software so that an executable program can be created for a computing environment that is different from the one for which it was originally designed...
to other platforms
Platform (computing)
A computing platform includes some sort of hardware architecture and a software framework , where the combination allows software, particularly application software, to run...
. The main Windows
Microsoft Windows
Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
version of the archiver
File archiver
A file archiver is a computer program that combines a number of files together into one archive file, or a series of archive files, for easier transportation or storage...
, known as WinRAR
WinRAR
WinRAR is a shareware file archiver and data compression utility developed by Eugene Roshal, and first released in autumn of 1993. It is one of the few applications that is able to create RAR archives natively, because the encoding method is held to be proprietary.-Developer:The current developer...
, is distributed as trialware, requiring payment after 40 days (although it can still be used after this period, albeit with nags); shareware
Shareware
The term shareware is a proprietary software that is provided to users without payment on a trial basis and is often limited by any combination of functionality, availability, or convenience. Shareware is often offered as a download from an Internet website or as a compact disc included with a...
versions of this program are also available for GNU/Linux, Mac OS X
Mac OS X
Mac OS X is a series of Unix-based operating systems and graphical user interfaces developed, marketed, and sold by Apple Inc. Since 2002, has been included with all new Macintosh computer systems...
, DOS
DOS
DOS, short for "Disk Operating System", is an acronym for several closely related operating systems that dominated the IBM PC compatible market between 1981 and 1995, or until about 2000 if one includes the partially DOS-based Microsoft Windows versions 95, 98, and Millennium Edition.Related...
, OS/2
OS/2
OS/2 is a computer operating system, initially created by Microsoft and IBM, then later developed by IBM exclusively. The name stands for "Operating System/2," because it was introduced as part of the same generation change release as IBM's "Personal System/2 " line of second-generation personal...
, and FreeBSD
FreeBSD
FreeBSD is a free Unix-like operating system descended from AT&T UNIX via BSD UNIX. Although for legal reasons FreeBSD cannot be called “UNIX”, as the direct descendant of BSD UNIX , FreeBSD’s internals and system APIs are UNIX-compliant...
, though they are all called simply "RAR".
RARLAB distributes the source code and binaries for a freeware command-line "unrar" program, although it is not under a free software
Free software
Free software, software libre or libre software is software that can be used, studied, and modified without restriction, and which can be copied and redistributed in modified or unmodified form either without restriction, or with restrictions that only ensure that further recipients can also do...
license. This program can only decompress/extract, not create RAR files.
Other software
- There is a free software decompression library called "unrarlib", licensed under the GPLGNU General Public LicenseThe GNU General Public License is the most widely used free software license, originally written by Richard Stallman for the GNU Project....
, based on an old version of unrar with permission from the author Eugene Roshal, but it can only decompress archives created by RAR versions up to 2.x. Archives created by RAR 2.9 and later (which are most RAR archives found today) use a different format which is not supported by the free library.
- Stuffit ExpanderStuffIt ExpanderStuffIt Expander is a proprietary, freeware, closed source, decompression software utility developed by Allume Systems . It runs in Mac OS Classic, Mac OS X, Microsoft Windows, and Linux x86/UNIX.As of November 2010, the latest Macintosh version is 2011 , which requires Mac OS X v10.5 or later...
(freeware associated with the paid-for StuffitStuffItStuffIt is a family of computer software utilities for archiving and compressing files on the Macintosh and Microsoft Windows platforms: it was originally produced for the Macintosh. An old version for Linux and Sun Solaris 2.7 or later is also available...
compression program) also decodes RAR files. - Free RAR Extract Frog (Windows freeware with instructions in 50+ languages) also decodes RAR files.
- The open source software archiver 7-Zip7-Zip7-Zip is an 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 Microsoft Windows shell integration. 7-Zip began in 1999 and is actively...
decompresses newer RAR files using a closed-source, free-of-charge plug-in under the "unRAR license"; the license makes the plug-in source-available but not free softwareFree softwareFree software, software libre or libre software is software that can be used, studied, and modified without restriction, and which can be copied and redistributed in modified or unmodified form either without restriction, or with restrictions that only ensure that further recipients can also do...
.
- The UnarchiverThe UnarchiverThe Unarchiver is a free data decompression frontend of libxad, which supports more formats than Archive Utility , 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. The latest...
is another open source unarchiver which can decompress newer RAR files.
- The free software Linux archivers File RollerFile RollerFile Roller is the archive manager of the GNOME desktop environment.-Features:File Roller Archive Manager can:* Create and modify archives.* View the content of an archive.* View a file contained in the archive.* Extract files from the archive....
, ArkArk (computing)Ark is an archiving tool for the KDE Software Compilation, included into kdeutils package.- Features :*Ark does not intrinsically understand any archive format, but instead acts as a frontend to command-line archivers...
, and XarchiverXarchiverXarchiver is a front-end to various command line archiving tools for Linux and BSD operating systems, designed to be independent of the desktop environment. It is the default archiving application of Xfce and LXDE....
can use the non-free unrarUnrarUnrar is the name of two different command-line applications for extracting RAR archives.-RARLAB UnRAR:This version of UnRAR is distributed by RARLAB, the makers of the commercial WinRAR archivers...
program to decompress RAR files, if they are found in the system path.
- Sharp IMG Viewer is a resource explorer developed using .NET Framework.NET FrameworkThe .NET Framework is a software framework that runs primarily on Microsoft Windows. It includes a large library and supports several programming languages which allows language interoperability...
for Microsoft WindowsMicrosoft WindowsMicrosoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
which can decompress RAR and other compressed file formats.
UnRAR.dll
UnRAR.Dll is a free of charge dynamic-link libraryDynamic-link library
Dynamic-link library , or DLL, is Microsoft's implementation of the shared library concept in the Microsoft Windows and OS/2 operating systems...
(DLL) that can be downloaded from the official WinRAR site. It is found under "Extras".
Comparison to other compression algorithms
RAR compression operations are typically slower than compressing the same data with early compression algorithms like ZIPZIP (file format)
Zip is a file format used for data compression and archiving. A zip file contains one or more files that have been compressed, to reduce file size, or stored as is...
but with a moderately better rate of compression.
7z
7z
7z is a compressed archive file format that supports several different data compression, encryption and pre-processing algorithms. The 7z format initially appeared as implemented by the 7-Zip archiver. The 7-Zip program is publicly available under the terms of the GNU Lesser General Public...
's LZMA
LZMA
The Lempel–Ziv–Markov chain algorithm is an algorithm used to perform data compression. It has been under development since 1998 and was first used in the 7z format of the 7-Zip archiver...
algorithm reaches a higher compression ratio than RAR, except for "multimedia" files like .wav and .bmp files where RAR uses specialized routines that outperform LZMA. Other free compression software such as NanoZip and FreeArc
FreeArc
FreeArc is a free and open source file archiver developed by Bulat Ziganshin.-Algorithms:FreeArc uses LZMA, PPMD, TrueAudio, Tornado and GRzip algorithms with automatic switching by file type, and also uses set of filters—for instance it can remove repetitions from text.-Archive size:In Tom's...
usually outperform WinRAR.
Optional creation of "recovery volumes" (.rev files) with redundancy data which can be used to reconstruct missing files in a volume set.
RAR file limitations
The minimum size of a RAR file is 20 bytes. The maximum size of a RAR file is 9,223,372,036,854,775,807 (263-1) bytes, which is 8 exabytes.See also
- Comparison of archive formatsComparison of archive formatsThere are many popular computer data archive formats for creating and maintaining archive files. The tables below compare many popular archive formats.-Purpose:The earliest use of archive formats was for backup, mobility, and archiving....
- List of archive formats
- Comparison of file archiversComparison of file archiversThe following tables compare general and technical information for a number of file archivers. Please see the individual products' articles for further information. They are neither all-inclusive nor are some entries necessarily up to date...
- UnrarUnrarUnrar is the name of two different command-line applications for extracting RAR archives.-RARLAB UnRAR:This version of UnRAR is distributed by RARLAB, the makers of the commercial WinRAR archivers...
Further reading
- RAR Archiver Frequently Asked Questions by Eugene Roshal
- RAR File format by WinRAR
- LAMPdocs: quick guide with annotation of the advantages of RAR in comparison to other file archivers
External links
- Official RAR site * Official RAR site is http://win-rar.com
- Subscription Online tool for opening rar files without software
- Freeware tool for opening rar files