gzip

Gzip is a data compression utility and file format designed to reduce the size of files. It was created as part of the GNU Project by Jean-Loup Gailly and Mark Adler and is distributed under the GNU General Public License. It is widely used on Unix-like systems and in software tools across platforms.

Gzip compresses individual files using the DEFLATE algorithm, a combination of LZ77 and Huffman coding. It produces files with a .gz extension; when used with tar, the result is a tar.gz or tgz archive. It also operates in streaming mode, allowing data to be compressed or decompressed in pipelines with other programs.

The gzip file format contains a header with optional metadata (such as the original file name and timestamp), followed by compressed data, and a trailer with a CRC-32 of the uncompressed data and the ISIZE field, which is the input size modulo 2^32. The format supports concatenated members, enabling multiple files to be stored in sequence in a single .gz file.

Common usage includes the gzip and gunzip commands, as well as piping through standard input and output. Compression levels range from 1 to 9, with -9 providing the best compression at the cost of speed; default is -6. Typical workflows involve creating archives with tar and gzip (for example, tar -czf) or decompressing with gzip -d. gzip is also widely used in web contexts to compress HTTP responses via the Content-Encoding: gzip mechanism, reducing bandwidth and improving transfer times.