RAR (file format)

RAR is a proprietary archive file format that supports data compression, error correction and file spanning. It was developed in 1993 by Russian software engineer Eugene Roshal and the software is licensed by win.rar GmbH. The name RAR stands for Roshal Archive.

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, the elder brother of Eugene Roshal, holds 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.

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 one byte less than 8 EiB.

The RAR file format revision history:

RARlab's native software is available for Microsoft Windows (named WinRAR), Linux, FreeBSD, macOS, and Android; archive extraction is supported natively in ChromeOS. WinRAR and RAR for Android support the graphical user interface (GUI); other versions named RAR run as console commands.

RAR files can only be created with proprietary WinRAR (Windows), RAR for Android, command-line RAR (available for Windows, 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.

Several programs can unpack the file format.