Gzip

File Format
Name	gzip
Ontology	Electronic File Formats Compression gzip
Extension(s)	.gz
MIME Type(s)	application/x-gzip
PRONOM	x-fmt/266

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: 0x1F 0x8B. The third byte indicates the compression method, and is normally 0x08 (meaning DEFLATE).

gzip 0.5 apparently used Freeze/Melt 1.x format, with signature bytes 0x1F 0x9E.

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++)

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