In computing, RAR (pronounced Rare or letter by letter) is a proprietary compressed archive format. Programs for creating and decompressing RAR archives are available for several platforms; the most popular such program is WinRAR.

The RAR format and archiver using the format (originally for DOS, and later ported to other platforms) were developed by Eugene Roshal. Eugene Roshal was born March 10, 1972 in Russia, graduated from Chelyabinsk Technical University . As well as releasing the archiver as shareware, he has also released source code for decoding RAR archives, under a licence that allows free distribution and modification, but forbids its use to build a compatible encoder. The encoding method is held to be proprietary.

The file extension is .rar. The MIME-Type is application/x-rar-compressed.

Comparison to other compression algorithms

RAR compression operations are typically slower than compressing the same data with ZIP and other compression algorithms, but better compression is achieved in most cases.

Archive features

Apart from better compression, RAR has several other features not usually found in other archive formats, which contribute to its popularity:

• Its handling of split volumes is very good. Few other compression formats have the ability not only to process volumes, but do it well. The most notable such format, before the advent of RAR, was ARJ.
• RAR archives can be of a solid format, in which all of the compressed files are treated as a single data block. This allows for better compression rates when the files in an archive have similarities, which is often the case when they are of the same format. One disadvantage of solid files is that, in order to extract a single file from an archive, all of the files stored before it have to be processed as well.
• It features strong encryption capabilities. Older versions of the file format used a proprietary but strong encryption algorithm; newer versions use the AES encryption algorithm, which is considered very strong by today's standards. The only ways to recover an encrypted file are via dictionary or brute force attacks, which are usually infeasible.
• Extra redundancy can be added to an archive, making it more resistant to corruption. Even if part of an archive is damaged, it may be possible to fully recover the stored data if a large enough recovery record exists.

Notes

The warez scene has adopted RAR as its file compression standard, much like the ARJ format in the 90s.

See also

• List of archive formats

External links

• Official site containing archivers for several platforms
• MacRAR
• UnRarX – UnRar for Mac OS X
• RAR add-ons – UnRAR for various platforms, including Eugene Roshal's source code
• Unrarlib – a library for decoding RAR (version 2) archives based on the Roshal's code, might be GPL compatible