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RAR (file format)

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RAR file format
Filename extension
.rar,.rev,.r00,.r01
Internet media type
application/vnd.rar
Uniform Type Identifier (UTI)com.rarlab.rar-archive
Magic number52 61 72 21 1A 07 00
(RAR 1.5 to 4.0)
52 61 72 21 1A 07 01 00
(RAR 5+)[1]
Size limitation263-1 bytes (almost 8exbibytes)
Developed byEugene Roshal
Initial releaseMarch 1993;31 years ago(1993-03)[2]
Type of formatarchive format
Open format?No (decompression source code available, but notfree software,due to restriction that it not be used to create RAR-compatible archives)
Websiterarlab

RARis aproprietaryarchive file formatthat supportsdata compression,error correctionandfile spanning.[3]It was developed in 1993 by Russian software engineerEugene Roshaland the software is licensed bywin.rar GmbH.[3]The nameRARstands forRoshal Archive.

File format

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Thefilename extensionsused by RAR are.rarfor the data volume set and.revfor 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.r00for the second, and then.r01,.r02,etc.

RAR compression applications and libraries (including GUI basedWinRARapplication for Windows, console rar utility for different OSes and others) are proprietary software, to which Alexander L. Roshal,[3]the elder brother ofEugene Roshal,owns the copyright. Version 3 of RAR is based onLempel-Ziv(LZSS) andprediction 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 is9,223,372,036,854,775,807(263−1) bytes, which is one byte less than 8EiB.[5]

Versions

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The RAR file format revision history:

  • 1.3 – the first public version, does not have the "Rar!" signature.
  • 1.5 – changes are not known.
  • 2.0 – released with WinRAR 2.0 and Rar for MS-DOS 2.0; features the following changes:
    • Multimedia compression for true color bitmap images and uncompressed audio.
    • Up to 1MBcompression dictionary.
    • Introduces archives data recovery protection record.
  • 2.9[note 1]– released in WinRAR version 3.00. Feature changes in this version include:
    • File extensions is changed from{volume name}.rar, {volume name}.r00, {volume name}.r01, etc.to{volume name}.part001.rar, {volume name}.part002.rar, etc.
    • Encryption of both file data and file headers.
    • Improves compression algorithm using 4MBdictionary size, Dmitry Shkarin'sPPMII algorithmfor file data.
    • Optional creation of "recovery volumes" (.rev files) forerror correction,which can be used to reconstruct missing files in a volume set.
    • Support for archive files larger than 9GB.
    • Support forUnicodefile names stored inUTF-16little endian format.
  • 5.0 – supported by WinRAR 5.0 and later. Changes in this version:
    • Maximum compression dictionary size increased to 1GB(default for WinRAR 5.x is 32MBand 4 MB for WinRAR 4.x).
    • Maximum path length for files in RAR and ZIP archives is increased up to 2048 characters.
    • Support forUnicodefile names stored inUTF-8format.
    • Faster compression and decompression.
    • Multicore decompression support.
    • Greatly improves recovery.
    • OptionalAESencryption increased from 128-bit to 256-bit.
    • Optional 256-bitBLAKE2file hash instead of a default 32-bitCRC32file checksum.
    • Optional duplicate file detection.
    • OptionalNTFShard and symbolic links.
    • Optional Quick Open Record. Rar4 archives had to be parsed before opening as file names were spread throughout the archive, slowing operation particularly with slower devices such as optical drives, and reducing the integrity of damaged archives. Rar5 can optionally create a "quick open record", a special archive block at the end of the file that contains the names of files included, allowing archives to be opened faster.
    • Removes specialized compression algorithms for Itanium executables, text, raw audio (WAV), and raw image (BMP) files; consequently some files of these types compress better in the older RAR (4) format with these options enabled than in RAR5.
  • 5.0+ – partially supported by WinRAR 5.0 and later. Fully supported by WinRAR 7.0 and later. Changes in this version:
    • Compression dictionary up to 64GB.
    • Improved compression by the addition of "Alternate search algorithm".
    • Maximum path length limit increased from 2047 to 65535 characters.
Notes
  1. ^WinRAR 5.0 and RAR for Android refer to this format as RAR4.

Software

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Main article:Comparison of file archivers

Operating system support

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Software is available forMicrosoft Windows(named WinRAR),Linux,FreeBSD,macOS,andAndroid;archive extraction is supported natively inChromeOS.WinRAR supports the Windowsgraphical user interface(GUI); other versions named RAR run as console commands. Later versions are not compatible with some older operating systems previously supported:

  • WinRARv6.10 supportsWindows Vistaand later.
  • WinRAR v6.02 is the last version that supportsWindows XP.[6]
  • WinRAR v4.11 is the last version that supportsWindows 2000.[6]
  • WinRAR v3.93 is the last version that supportsWindows 95,98,ME,andNT 4.0.[6]
  • WinRAR 2.06 is the last version to support Windows 3.1, Windows NT 3.1, Windows NT 3.5, Windows NT 3.51 and Win32s.
  • RAR v3.93 is the last version that supportsMS-DOSandOS/2on 32-bitx86CPUs such as80386and later. It supports long file names in a Windows DOS box (except Windows NT), and uses theRSXDPMIextender.[7]
  • RAR v2.50 is the last version that supports MS-DOS and OS/2 on 16-bit x86 CPUs such asIntel 8086,8088,and80286.[7]

Creating RAR files

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RAR files can be created legally only with commercial softwareWinRAR(Windows), RAR[8]for Android,command-lineRAR (Windows, MS-DOS, macOS, Linux, and FreeBSD), and other software that has written permission from Alexander Roshal or uses copyrighted code under license from Roshal. The software license agreements forbid reverse engineering.[3]

Third-party software for extracting RAR files

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Several programs can unpack the file format.

  • RARLAB distributes theC++source code and binaries for a command-lineunrarprogram.[9]The license permits its use to produce software capable of unpacking, but not creating, RAR archives, without having to pay a fee. It is not afree softwarelicense.
  • 7-Zip,afree and open-sourceprogram, starting from 7-Zip version 15.06 beta[10]can unpack RAR5 archives, using the RARLAB unrar code.
  • PeaZipis a free RAR unarchiver, licensed under theLGPL,it runs as a RAR extractor on Linux, macOS, and Windows, with a GUI. PeaZip supports both pre-RAR5.rar files, and files in the new RAR5 format.[11]
  • The Unarchiveris a proprietary freeware software unarchiver for Mac for RAR and other formats. It was previouslyfree softwarelicensed under theLGPL,up to version 3.11.1 (released 2016), which at the time provided a free-software implementation of extraction of RAR versions up to RAR5.[12][13][14][15]There is a free software (LGPL) command-line version,unar,from 2016, which runs on Mac, Windows, and Linux.[16][17]
  • UNRARLIB (UniquE RAR File Library)[18]was an obsolete free software unarchiving library called "unrarlib", licensed under theGPL.It could only decompress archives created by RAR versions prior to 2.9; archives created by RAR 2.9 and later use different formats not supported by this library. The original development-team ended work on this library in 2007.[19][20][18]
  • libarchive, a free and open-source library for reading and writing a variety of archive formats, supports all RAR versions, including RAR5.[21]The code was written from scratch using RAR's “technote.txt” format description.[22]
  • Microsoftannounced (May 23, 2023)[23]native support for additional archive formats inWindows 11,including tar, 7-zip, rar, gz and many others using thelibarchiveopen-source project. Recently (July 16, 2023), there have been Insider builds that have native support. It’s said to come out in version 23H2.

Other uses ofrar

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The filename extensionraris also used by the unrelatedResource Adapter aRchivefile format.[24][25][26][27][28][29]

See also

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References

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  1. ^RAR 5.0 technote
  2. ^"Interview by correspondence"(in Russian). 1997–2002.Retrieved26 April2010.
  3. ^abcdwin.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".Retrieved2013-05-01.
  6. ^abcWinRAR Release History; RARsoft.
  7. ^ab"FreeDOS general questions".Archived fromthe originalon 2014-10-11.Retrieved2014-10-07.
  8. ^"RAR - Apps on Google Play".play.google.Retrieved2019-01-31.
  9. ^"RarLab downloads: freeware UnRAR source and binaries download".RarLab.The license states: "The source code of UnRAR utility isfreeware".
  10. ^"7-Zip / Discussion / Open Discussion: 7-Zip 15.06 beta".sourceforge.net.Retrieved2015-10-24.
  11. ^PeaZip websitewith info about RAR5 extraction.
  12. ^"The Unarchiver".The Unarchiver.Archived fromthe originalon 2017-06-21.
  13. ^"Another High Priority Project done: The Unarchiver provides free RARv3 extraction tools".Free Software Foundation.Retrieved2024-02-18.
  14. ^"The Unarchiver changes".The Unarchiver.Archived fromthe originalon 2017-07-06.
  15. ^"The Unarchiver source code from 2016 is licensed under the GNU Lesser General Public License v2.1".GitHub.2011-05-11.Retrieved2024-02-18.
  16. ^"Unar and Lsar - Command Line Tools for The Unarchiver".The Unarchiver.Retrieved2024-02-18.,including The Unarchiver source code from 2016.
  17. ^"MacPaw/XADMaster is licensed under the GNU Lesser General Public License v2.1".GitHub.2018-03-21.Retrieved2021-11-23.
  18. ^ab "Home".UnRarLib.org.UniquE RAR File Library. 2007.
  19. ^"Features".UnRarLib.org.UniquE RAR File Library. 2002.
  20. ^"FAQ".UnRarLib.org.UniquE RAR File Library. December 2011.
  21. ^"List of formats supported by libarchive".GitHub.Retrieved2021-05-01.
  22. ^"Support for RAR · Issue #151 · libarchive/Libarchive".GitHub.
  23. ^Panay, Panos (2023-05-23)."Bringing the power of AI to Windows 11 – unlocking a new era of productivity for customers and developers with Windows Copilot and Dev Home".Windows Developer Blog.Retrieved2023-05-26.
  24. ^"The Java EE 5 Tutorial".Retrieved2017-12-02.
  25. ^"RAR abbreviation stands for Resource Adapter Archive".Retrieved2017-12-02.
  26. ^"Resource Adapter aRchive - How is Resource Adapter aRchive abbreviated?".Retrieved2017-12-02.
  27. ^"9 Packaging and Deploying Resource Adapters".Retrieved2017-12-02.
  28. ^"Apache Maven RAR Plugin".Retrieved2017-12-02.
  29. ^"java - Is Resource Adapter Archive (RAR) the same as Roshal ARchive (RAR)? - Stack Overflow".Retrieved2017-12-02.
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