RAR extension designates a
popular
archive format introduced by RarLab's program WinRAR (shareware
file archiving utility, free for 40 days) for
Microsoft Windows platform; the software was ported to Linux (only as
extractor) by the same Author, Eugene
Roshal. Initial application release dates back to 1995, last RAR5
standard revision is from 2013.
RAR
format is well
known for the high
compression ratio - superior compared to
zip, comparable with 7z format and zipx format - being the compressor
based
on Lempel-Ziv (LZSS)
algorithm and prediction by partial matching (PPMd, Dmitry Shkarin).
RAR standard also features strong file encryption by
design
-
encrypted RAR4 archives rely on AES-128 based
encryption
-
encrypted RAR5 archives rely
on AES-256 in CBC
mode, with improved key
scheduling, and can optionally use cryptographically strong 256-bit
BLAKE2sp hash instead of CRC32 checksum to verify integrity of files inside
archives
Notably, .rar
format features advanced error
correction / data
recovery capabilities setting optional recovery records during archive
creation (from WinRar).
Please note RAR4 and RAR5 standard revisions both have same .rar
extension, the format revision level being declared in file header area.
Spanned multi-volume rar archives are designed by R01 extension - with
file extension numerator incremented for following volumes of the set.
RAR format was designed ground up to avoid practical limitations in terms
of size and number of items in archive:
Maximum size of
a RAR archive
RAR file can be large
up to 2^63 bytes in size (8 exabytes of
total size of the archive, signed 64 bit integer of filesize field),
far exceeding current needs and
capabilities of most filesystems.
To work with input
files, or output archives, larger than 4 GB, FAT32 filesystem
should be avoided (limited to files smaller than 2^32 bytes).
Both NTFS and exFAT
filesystems allows maximum file size up to 2^64 byte (16 exabyte),
large enough to accomodate largest possible rar format file size -
theoretically, as current implementations are limited to smaller max
file sizes.
Maximum number of files in a
RAR archive
RAR file can
contain up to 2^31 files (max 2 billion files, signed 32
bit integer for file number filed), which makes rar format suitable for
archiving large number of files and directories, especially if compared
to competing early ZIP standard limited to 64K maximum files (2^16).
PeaZip free
archiver features
read support to open and extract RAR files
through Open Source unrar components from 7z/p7zip, and can convert
existing
.rar archives into any write supported archive format, providing an
Open Source alternative to WinRar for extraction of rar archives.
Also, PeaZip can create RAR files
through WinRar if available on the machine - autonomous support to rar
compression is not possible due to RarLab's rar format licensing
limitations.
Optionally, the program allows managing RAR5 file type with separate UNRAR / UNRAR5 Plugin based on RarLab's
unrar
code - not mandatory, PeaZip can natively handle RAR5 standard out of
the box.
Online resources about rar file type: WinRar official
domain, RAR
format Wikipedia
entry, what is error
correction, 7-Zip
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RAR
file type is proprietary, even if the format specifications are well
documented and unrar (extraction) code is available for free, it is
encumbered by no reverse engineering
clause about using sources to create a rar compressor. |
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No Open
Source RAR implementation (with full read / write support) is
consequently known to be able to fully replace WinRar. Anyway PeaZip
can write to RAR format (create new rar archives, and edit existing
archives - add, delete, update) using WinRar
executable, if installed, without leaving the application - this works
simply setting Rar.exe as custom compressor utility in PeaZip.
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.RAR
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Author
Eugene Roshal, 1995
max
2 billion files per rar archive (2^31), 8 EB maximum size of rar
archive (2^63 bytes) |
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SPEED 
Rar format speed is good: even employing powerful advanced comperssion
techniques, handling
the format is remarkably efficient in terms of speed.
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COMPRESSION
RATIO
Rar format features high compression ratio, comparable to WinZip's zipx
but slightly inferior to 7-Zip's 7z
with most common real-world data sets. |
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ADVANCED
OPTIONS 
Excellent, Rar standard provides a wide array of advanced features.
Most notable feature is native support for recovery records,
that allows to recover archives from moderate corruption states.
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Synopsis: What is RAR
format. What are .rar archives, native WinRar archive type, specs. What
are rar file type limitations in terms of maximum archive size,
max number of items in archive and max size of file in archive. RAR
file format specifications, features and advantages for compression
ratio, and advanced features such recovery records and AES encryption.
Topics: rar file
extension specs
PeaZip > FAQ >
What is RAR file format (WinRar archives)
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