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GZ file .gz
File format · Released 1992 · By Jean-loup Gailly & Mark Adler

About GZ Files

Gzip Compressed

Gzip is a single-file compression format based on the DEFLATE algorithm. It is most commonly paired with TAR to create .tar.gz archives and is the standard compression for web content delivery.

Family

Archives & Compressed

Extension

.gz

MIME Type

application/gzip

Can Use As

Input Output
● Hex Magic-Bytes Signature (Offset 0x00) Archives & Compressed Binary/Text Stream
47 5A 46 4D 00 01 00 00 4B 41 49 4A ASCII: GZFM....KAIJ
WASM + ISO-27001 HYBRID ENGINE
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Lossless JPEG Q100 + standard COM segment padding for government & exam portals

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The story

HOW GZ CAME TO BE.

1951
1992

gzip was born in 1992 when Jean-loup Gailly and Mark Adler needed a free, unpatented alternative to Unix compress (whose LZW algorithm was covered by the same Unisys patent that haunted GIF). They published gzip 1.0 under GPL in October 1992 using a DEFLATE algorithm — a combination of LZ77 and Huffman coding — that became RFC 1951.

gzip quickly became the default compressor on every Unix-like system. The .gz file extension wraps any single file in DEFLATE compression. Pair it with tar and you get .tar.gz (or .tgz), the most common Unix release format. Mark Adler went on to write the zlib library that every modern platform uses; Jean-loup Gailly maintained gzip for decades. Today DEFLATE underpins ZIP, PNG, HTTP Content-Encoding, and dozens of other formats — a humble 1992 algorithm quietly doing the compression for most of the internet.

ISO / MIME SPECS

Technical Specifications

MIME type
application/gzip
Extensions
.gz, .tgz (with tar)
Algorithm
DEFLATE (LZ77 + Huffman coding)
Standard
RFC 1952 (gzip), RFC 1951 (DEFLATE)
Header
10 bytes: magic, method, flags, mtime, extra, filename, comment, crc, isize

Typical Sizes & Weights

Plain text file

25-40% of original

HTML page

20-30% of original

Source code archive

15-30% of original

Already-compressed file (JPEG, MP4)

99-100% (no gain)

STRENGTHS & LIMITATIONS.

Strengths

  • Patent-free, royalty-free — that was the whole point in 1992.
  • Universally supported on every OS.
  • Fast compression and extremely fast decompression.
  • Preserves original timestamps and filenames in the header.
  • Streamable — can compress/decompress over pipes.

Limitations

  • Compresses one file at a time — needs tar for multi-file archives.
  • Older algorithm — Zstandard, xz, and brotli all beat it on ratio.
  • Single-threaded in the reference implementation (pigz fixes this).
  • Not as aggressive as modern codecs on highly redundant data.

CURIOSITIES & TRIVIA.

01

gzip's DEFLATE algorithm is the same compression used inside ZIP, PNG, and HTTP Content-Encoding — it powers most of the web.

02

Mark Adler also wrote zlib, the library every modern platform uses to implement gzip — his name is baked into iOS, Android, Windows, macOS, and Linux.

03

Every Linux man page (/usr/share/man/) is shipped as a .gz file and decompressed on demand.

04

HTTP servers send gzipped responses billions of times per second — the "Accept-Encoding: gzip" header is in every request you make.

05

gzip refuses to compress a file if the result would be larger than the input — it silently stores uncompressed.

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STUDIO TOOLS FOR GZ

Specialized Utilities for .GZ Files

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CONVERT FROM GZ

Common Use Cases

Web content compression, tar.gz archives, log file compression.

Related Formats

Popular comparisons

Popular GZ conversions

The most-requested destinations when starting from GZ.

Frequently Asked Questions

GZ (Gzip Compressed) is an archive format used to bundle multiple files and folders into a single compressed file. The archive preserves the directory structure and typically reduces total size via compression. GZ sits in the archives & compressed family and has specific strengths around compression ratio, speed, or platform support.

7-Zip, WinRAR, The Unarchiver (macOS), and the built-in archive utilities on Windows and macOS open most GZ files. For command-line extraction, 7z, unar, or the format-specific tool handles GZ cleanly. If your extractor does not recognise GZ, convert to ZIP first — ZIP opens on every operating system without extra software.

Upload the GZ to KaijuConverter and pick ZIP, 7Z, TAR.GZ, or RAR as the target. Our pipeline extracts the original archive and re-compresses the contents into the target format. File permissions, timestamps, and directory structure are preserved where both formats support them.

Depends on the goal. ZIP is the universal baseline — every OS extracts it out of the box. Formats like 7Z or TAR.GZ compress better but require specific tools. GZ may win on compression ratio, password support, or OS integration for specific workflows; ZIP wins on raw compatibility.

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