zlib

A Massively Spiffy Yet Delicately Unobtrusive Compression Library
(Also Free, Not to Mention Unencumbered by Patents)

(Not Related to the Linux zlibc Compressing File-I/O Library)

Welcome to the zlib Home Page, maintained by Greg Roelofs (on disk space provided by Walnut Creek CD-ROM). If this page seems suspiciously similar to the PNG Home Page, rest assured that the similarity is completely coincidental. No, really.

Current release:

zlib 1.1.3

NOTE: internal mirroring at www.cdrom.com has been broken since the end of April 1999; the latest version of the zlib home page is available only from ftp.cdrom.com or any of its mirror sites).

Canonical URL: ftp://ftp.cdrom.com/pub/infozip/zlib/zlib.html (California, USA)

Mirror sites (see CTAN mirror list for more):

[DDJ's zlib image] zlib is designed to be a free, general-purpose, legally unencumbered -- that is, not covered by any patents -- lossless data-compression library for use on virtually any computer hardware and operating system. The zlib data format is itself portable across platforms. Unlike the LZW compression method used in Unix compress(1) and in the GIF image format, the compression method currently used in zlib essentially never expands the data. (LZW can double or triple the file size in extreme cases.) zlib's memory footprint is also independent of the input data and can be reduced, if necessary, at some cost in compression. A more precise, technical discussion of both points is available on another page.

zlib was written by Jean-loup Gailly (compression) and Mark Adler (decompression). Jean-loup is also the primary author/maintainer of gzip(1), the author of the comp.compression FAQ list and the former maintainer of Info-ZIP's Zip; Mark is also the author of gzip's and UnZip's main decompression routines and was the original author of Zip. Not surprisingly, the compression algorithm used in zlib is essentially the same as that in gzip and Zip, namely, the `deflate' method that originated in PKWARE's PKZIP 2.x.

Mark and Jean-loup can be reached by e-mail at zlib@gzip.org .

Greg, Mark and/or Jean-loup will add some more stuff here when they think of something to add. For now this page is mainly a pointer to zlib itself and to the official zlib and deflate documentation. Note that the specifications both achieved official Internet RFC status in May 1996, and zlib itself was adopted by JavaSoft in version 1.1 of the Java Development Kit (JDK), both as a raw class and as a component of the JAR archive format.

The lovely zlib-vise image above was provided courtesy of Bruce Gardner, art director of Dr. Dobb's Journal. It appears in Mark Nelson's article in the January 1997 issue (see below).

The source code for the current release is publicly available at several locations:

* zlib source code, version 1.1.3, gzip'd tar format (168k):

* US (California) (also via ftp)
* US (Virginia)
* France

* zlib source code, version 1.1.3, zipfile format (219k):

* US (California) (also via ftp)
* US (Virginia)
* France

Version 1.1.3 fixes a number of buglets in the gz* functions and one ``inflate input-buffer bug that shows up on rare but persistent occasions''; it also adds a number of new contrib items, including 586 and 686 assembler routines. See the ChangeLog for details.

Note that zlib is an integral part of libpng and has been tested extensively as part of many PNG-supporting applications. Upcoming versions of gzip and UnZip will also use zlib.

Related Links

* zlib Frequently Asked Questions
* zlib Manual [New!]
* zlib Technical Details
* zlib-Related Specifications
* zlib's Deflate Algorithm
* zlib License

* Mark Nelson's ZlibTool article and source code for Dr. Dobb's Journal (January 1997)
* zlib for Linux, both shared and static plus headers (RPM format; many architectures)
* zlib for HP-UX 10.20 and 11.00 (shared library and headers)
* zlib for Windows 9x/NT (DLL version, plus related utilities)
* zlib for Windows 9x/NT (DLL and static version, 88k)
* zlib for BeOS R3 and R4
* zlib for Macintosh
* zlib for OS/2 (DLL and static version for emx 0.9c, 46k)
(click here if link breaks)
* zlib for Palm Pilot (alpha-level port of version 1.0.4, 28KB)
* zlib 32-bit OCX and 16-bit DLL (Visual Basic interface, source code and binaries, 84k)
* zlib 32-bit OCX (C++ source and binaries for use with Visual Basic 4.x or Delphi 2.0)
(unsupported VB5 binary also available)
* zlib Pascal port (Pascal source, tested with Turbo Pascal 7.0 and Delphi 3.02)
(not tested by us, but looks complete and up to date--version 1.1.2 at last check)
* zlib Perl interface (source code; look for Compress-Zlib*.tar.gz)
* zlib Python interface (online manual; part of the standard library as of Python 1.5)
* zlib Tcl interface (online manual; see the Download link)
* zlib Java interface (see also JAR format)
* Mark Nelson's JavaZip article (with source code) for Dr. Dobb's Journal (December 1997)
* Gilles Vollant's zlib-based mini-zip and mini-unzip
(see also Info-ZIP's UnZip, which optionally can be compiled with zlib)
* Scott Ludwig's zlib-based CExe executable compressor for Win32

* zlib information in Japanese
* Real World Scanning and Halftones (second edition includes a section on zlib)

* Markus Oberhumer's LZO `real-time' data compression library
(not tested by us, but looks like a good alternative if you need more speed and less compression)
* PPP Deflate Protocol (RFC 1979)
* Info-ZIP Home Page
* Portable Network Graphics (PNG) Home Page
* gzip Home Page
* Compression Pointers
* comp.compression Frequently Asked Questions list

Send comments or questions about zlib to the authors at zlib@gzip.org .
Please report broken links to newt@pobox.com . Last modified 13 December 1999, you betcha.

zlib software copyright © 1995-1998 Jean-loup Gailly and Mark Adler.
Web page copyright © 1996-1999 Greg Roelofs.