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RAR Archive File Format, Version 5

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Format Description Properties Explanation of format description terms

Identification and description Explanation of format description terms

Full name RAR Archive File Format, Version 5
Description

RAR5, or the Roshal ARchive format version 5, the current version (as of April 2017), was released in April 2013 and is supported by WinRAR 5.0 and later. See RAR_Family for details on the file structure.

There are significant changes in the format structure, compression algorithm and encryption algorithm.

Format changes:

  • Time stamps are stored as Coordinated Universal Time (UTC) instead of former local time
  • File names and archive comments are stored in UTF-8 encoding format
  • Change to 256 bit length BLAKE2sp hash instead of 32 bit CRC32 checksum
  • Maximum path length is increased up to 2048 characters.
  • Maximum comment length for RAR archives is increased from 64 to 256 KB
  • Includes the optional "quick open information" to allow the archive contents to open faster in WinRAR.

Compression algorithm changes:

  • Maximum compression dictionary size is increased up to 1 GB in 64 bit WinRAR. 32 bit WinRAR version can use up to 256 MB dictionary when creating an archive. Both 32 bit and 64 bit versions can unpack archives with any dictionary size, including 1 GB
  • Increased default dictionary size to 32 MB resulting in a higher compression ratio and faster speed over RAR4 (which had 4 MB).
  • Includes Intel IA-32 executable and delta compression algorithms
  • Removes supports for specialized text, multimedia, and Itanium executables compression algorithms

Encryption algorithm changes:

  • Encryption algorithm is changed from AES-128 (in RAR4) to AES-256
  • Increased default dictionary size to 32 MB resulting in a higher compression ratio and faster speed over RAR4 (which had 4 MB).
  • Changes in special password verification values allow many wrong passwords to be detected without having unpack the entire file
Production phase See RAR_Family
Relationship to other formats
    Subtype of RAR_Family, RAR Archive File Format Family
    Has earlier version RAR4, RAR Archive File Format, Version 4

Local use Explanation of format description terms

LC experience or existing holdings See RAR_Family.
LC preference None

Sustainability factors Explanation of format description terms

Disclosure Proprietary format with limited public information.
    Documentation The full specification is not publicly available but file structure information for RAR5 is available through the RARLab website.
Adoption See RAR_Family
    Licensing and patents See RAR_Family
Transparency See RAR_Family
Self-documentation See RAR_Family
External dependencies See RAR_Family
Technical protection considerations See RAR_Family

Quality and functionality factors Explanation of format description terms

Other
Bundling/compression See RAR_Family

File type signifiers and format identifiers Explanation of format description terms

Tag Value Note
Filename extension See note.  See RAR_Family
Internet Media Type See note.  See RAR_Family
File signature Hex: 52 61 72 21 1A 07 01 00
ASCII: Rar!
From Gary Kessler's File Signature Table and RAR 5.0 archive format tech note.
Pronom PUID fmt/613
See http://www.nationalarchives.gov.uk/PRONOM/fmt/613 for RAR5
Wikidata Title ID See note.  See RAR_Family.

Notes Explanation of format description terms

General

According to WinRAR version information, "older software including older WinRAR versions is not able to decompress RAR 5.0 archives, so if you plan to send an archive to other people, it is necessary to take the compatibility issue into consideration. You can select "RAR" instead of "RAR5" option in archiving dialog to create RAR 4.x archives compatible with previous WinRAR versions."

History  

Format specifications Explanation of format description terms


Useful references

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Last Updated: 07/11/2017