Gzip

gzip is a compressed file format and command line utility used primarily on Unix-style operating systems, but available cross-platform. It uses DEFLATE compression.

Identification
gzip files begin with two signature bytes:. The third byte indicates the compression method, and is normally  (meaning DEFLATE).

gzip 0.5 apparently used Freeze/Melt 1.x format, with signature bytes.

Specifications

 * RFC 1952

Software

 * Original gzip
 * GNU gzip
 * 7-Zip
 * zlib
 * zopfli (Gzip-compatible, better compression, but very slow compression)
 * Tiny gzip decompressor without using zlib (C++)

See also DEFLATE.

Links

 * Wikipedia article
 * Dissecting the GZIP format
 * Chart of format
 * How are zlib, gzip and Zip related? What do they have in common and how are they different? - Response to StackOverflow question by zlib/gzip co-creator Mark Adler