FixFile
File Format

GZ (.gz)

GNU Zip compression format using the Deflate algorithm. Used to compress single files on Unix/Linux systems and as the compression layer in .tar.gz archives.

Extension
.gz
MIME Type
application/gzip

Last updated

Overview

GZ (GNU Zip) is a file compression format using the Deflate algorithm, developed by Jean-loup Gailly and Mark Adler as a free replacement for the patent-encumbered Unix compress command. Released in 1992, gzip (GNU Zip) became the standard compression utility on Unix/Linux systems.

GZ compresses a single file — it cannot bundle multiple files like ZIP or TAR. This is why GZ is almost always combined with TAR for distributing multiple files as .tar.gz (often pronounced "tar-gee-zee" or "tarball"). GZ is also used as HTTP content encoding: web servers compress responses with gzip to reduce bandwidth, and browsers transparently decompress them.

Common Uses

  • Single file compression — compressing large text files, logs, and database dumps on Linux
  • Log rotation — Linux systems automatically compress old log files as .gz with logrotate
  • HTTP compression — web servers serve gzip-compressed HTML, CSS, and JavaScript for faster page loads
  • Combined with TAR — .tar.gz archives for distributing multiple files on Linux/Unix
  • Database backups — MySQL and PostgreSQL dump files are commonly gzip-compressed

Advantages

  • Fast compression/decompression — Deflate algorithm balances speed and ratio well
  • Universal Linux support — gzip is installed on every Linux and macOS system by default
  • Streaming-capable — compresses and decompresses in a single pass, suitable for pipes and streams
  • Good text compression — particularly effective on text files (source code, logs, HTML), achieving 60–80% reduction

Limitations

  • Single file only — cannot compress multiple files without TAR
  • Lower ratios than bzip2/xz — gzip prioritises speed; bzip2 and xz achieve better compression at the cost of speed
  • No integrity headers for content — gzip verifies the compressed data with CRC32 but does not checksum the original file independently

Supported Software

  • Linux/macOS: gzip, gunzip, zcat (all built-in)
  • Windows: 7-Zip, PeaZip, WinRAR, WSL
  • Programmatic: Python gzip module, Java GZIPInputStream, Node.js zlib

Tools for GZ files