File with a .RAR extension contains a RAR compressed archive of one or several files. It may also be a part of a divided archive or a whole volume of an archive. The extension filename is an abbreviation of Roshal Archive – name of the author of the algorithm and format – Eugene Roshal.

RAR compression is of a higher compression level than the ZIP format, it is used also in the 7z format. Many different programs support it. If an archive is divided, it may also have .R00, .R01 and other extensions.