RAR (file format)

RAR file format
Filename extension .rar, .rev, .r00, .r01
Internet media type application/x-rar-compressed
Uniform Type Identifier (UTI) com.rarlab.rar-archive
Magic number 52 61 72 21 1A 07 00
(RAR 1.5 to 4.0)
52 61 72 21 1A 07 01 00
(RAR 5+) [1]
Developed by Eugene Roshal
Initial release March 1993 (1993-03)[2]
Type of format archive format
Open format? No (decompression source code is available, but it's not free software due to the restriction that it must not be used to reverse engineer the RAR compression algorithm)

RAR is a proprietary[3] archive file format that supports data compression, error recovery and file spanning. It was developed by a Russian software engineer, Eugene Roshal (the name RAR stands for Roshal Archive) and the RAR software is licensed by win.rar GmbH.[3]

File format

The filename extensions used by RAR are .rar for the data volume set and .rev for the recovery volume set. Previous versions of RAR split large archives into several smaller files, creating a "multi-volume archive". Numbers were used in the file extensions of the smaller files to keep them in the proper sequence. The first file used the extension .rar, then .r00 for the second, and then .r01, .r02, etc.

RAR compression applications and libraries (including GUI based WinRAR application for Windows, console rar utility for different OSes and others) are proprietary software, to which Alexander L. Roshal,[3] the elder brother of Eugene Roshal, owns the copyright. 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.[4]

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 exbibytes minus 1 byte.[5]

Versions

The RAR file format revision history:

1 WinRAR 5.0 and RAR for Android refer to this format as RAR4.

Software

Operating system support

Software is available for Microsoft Windows (named WinRAR), Linux, FreeBSD, Mac OS X, and Android; archive extraction is supported natively in Chrome OS. WinRAR supports the Windows Graphical User Interface (GUI); other versions named RAR run as console commands. Later versions are not compatible with some older operating systems previously supported:

Creating RAR files

RAR files can be created only with commercial software WinRAR, RAR, and other software that has written permission from Alexander Roshal or shares copyrighted code under license from Alexander Roshal. The software license agreements forbid reverse engineering.[3] However, the fully open source program The Unarchiver, with support for uncompressing RAR archives, is distributed under the LGPL without any such restriction against reverse-engineering; it is possible that it could be a starting point for writing software capable of creating RAR archives. Graphical WinRAR is available for Windows. Console RAR application is available for Mac OS X, Linux, FreeBSD. Only WinRAR for Windows and Rar for Linux are available as native 64-bit applications. There is a native fully functional Android application called "RAR for Android".[8]

Extracting RAR files

Several programs can unpack the file format. RARLAB distributes the source code and binaries for a freeware command-line "unrar" program,[9] although this code is not under a free software license. This program can decompress/extract, but not create, RAR files. As of November 2014 some 3rd-party programs documented as "supporting the RAR format" did not recognise RAR5 files.

See also

References

  1. ↑ RAR 5.0 technote
  2. ↑ "Interview by correspondence" (in Russian). 1997–2002. Retrieved 26 April 2010.
  3. 1 2 3 4 win.rar GmbH. "RAR and WinRAR END USER LICENSE AGREEMENT (EULA)". RARLAB. The author and holder of the copyright of the software is Alexander L. Roshal. [...] Neither RAR binary code, WinRAR binary code, UnRAR source or UnRAR binary code may be used or reverse engineered to re-create the RAR compression algorithm, which is proprietary, without written permission.
  4. ↑ Christian Scheurer (2006-12-17). "unrarlib FAQ".
  5. ↑ "WinRAR description". Retrieved 2013-05-01.
  6. 1 2 WinRAR Release History; RARsoft.
  7. 1 2 FreeDOS general questions.
  8. ↑ RAR for Android; RARsoft.
  9. ↑ "freeware UnRAR source and binaries download". RarLab.com.
  10. ↑ The Unarchiver Website contains unar. Accessed 5 February 2013.
  11. ↑ Free Software Foundation on The Unarchiver
  12. ↑ "7-Zip / Discussion / Open Discussion: 7-Zip 15.06 beta". sourceforge.net. Retrieved 2015-10-24.

External links

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