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gzip

The classic Unix compression utility.

gzip uses the DEFLATE algorithm — the same one used in zip, png, and zlib — to compress and decompress files. It has been the default compression on Linux for decades, even though newer tools like xz, zstd, and lz4 offer better ratios or better speeds on modern CPUs. Most users never reach for gzip explicitly: tar -z, "rsync -z", apt-get's transport compression, and many other tools call it under the covers.

Jean-loup Gailly and Mark Adler wrote gzip in the early 1990s as a free replacement for the proprietary compress utility that shipped with Unix at the time. The same authors also wrote zlib, which is the library form of the same algorithm and is embedded in essentially every modern operating system, web server, and image-processing toolkit.

gzip is GPL-3.0-or-later and is maintained as a GNU project. The codebase is mature and rarely changes; modern versions emphasise correctness and security rather than algorithmic innovation. Despite the rise of zstd and its compression ratio, gzip's universality keeps it relevant.

Already preinstalled on every Linux system.