7-Zip is an open source file archiver with the high compression ratio for ZIP and GZIP formats, It's a free alternative to the popluar shareware archivers WinRAR and WinZip. It uses its own 7z archive format, but can read and write many other archive formats and offers a significantly higher compression ratio than its peers - up to 40% higher. It is developed by Igor Pavlov and was first released in 1999.
By default, 7-Zip creates 7z-format archives with a .7z file extension. Each archive can contain multiple directories and files. As a container format, security or size reduction are achieved using a stacked combination of filters. These can consist of pre-processors, compression algorithms, and encryption filters.
The core 7z compression uses a variety of algorithms, the most common of which are bzip2, PPMd, LZMA2, and LZMA. Developed by Pavlov, LZMA is a relatively new system, making its debut as part of the 7z format. LZMA uses an LZ-based sliding dictionary of up to 4 GB in size, backed by a range coder.
