7-Zip is an open-source file archiver, an application used primarily to compress files. 7-Zip uses its own 7z archive format, but can read and write several other archive formats. The program can be used from a command-line interface as the command p7zip, as a graphical user interface, or with a window-based shell integration. 7-Zip began in 1999 and is developed by Igor Pavlov. 7-Zip is open-source software. Most of the source code is under the GNU LGPL license. The unRAR code is under the GNU LGPL with an "unRAR restriction", which states that developers are not permitted to use the code to reverse-engineer the RAR compression algorithm.