WinRAR is a shareware file archiver and compressor utility for Windows. It can create archives in RAR or ZIP file formats,and unpack numerous archive file formats. There is an Android app called "RAR for Android", and command-line versions called "RAR" and "UNRAR" (widely released since autumn of 1993), available for Mac OS X, Linux, FreeBSD, Windows console mode, and MS-DOS.
WinRAR and the RAR file format has evolved over time. Starting with WinRAR version 5, support for a new archive format RAR5 was added, incompatible with the previous one, but also using the same RAR file extension.With the introduction of RAR5, the older RAR file format is now referred to as RAR4. WinRAR version 5 can read or write RAR4 or RAR5 archives, but older WinRAR doesn't support RAR5 archives.
The new RAR5 file format added numerous features, but removed comments for each file (though archive comment still remains), authenticity verification, and compression algorithms for specialized text and multimedia. RAR5 also changed the file name for split volumes from "archivename.rNN" to "archivename.partNN.rar".
The RAR5 file format increased the maximum dictionary size to 1 GB, thus allowing a WinRAR user to choose between 11 different compression directory sizes from 1 MB to 1GB. The default directory size in WinRAR version 5 was increased from 4 MB to 32 MB typically resulting in higher compression ratio, though the user can change the default setting back to 4 MB.
RAR5 also enhanced or added optional features: optional AES encryption was increased from 128-bit to 256-bit, option for 256-bit BLAKE2 file hashing algorithm (instead of default 32-bit CRC32), optional duplicate file detection, optional NTFS hard and symbolic links, optional Quick Open Record to allow large archives to be opened faster, maximum path length for files in RAR and ZIP archives is increased up to 2048 characters.