Skip site navigation (1)Skip section navigation (2)

FreeBSD Manual Pages


home | help
ZLIB(3)			   Library Functions Manual		       ZLIB(3)

       zlib - compression/decompression	library

       [see zlib.h for full description]

       The  zlib  library  is a	general	purpose	data compression library.  The
       code is thread safe, assuming that the standard library functions  used
       are  thread  safe, such as memory allocation routines.  It provides in-
       memory compression and  decompression  functions,  including  integrity
       checks  of the uncompressed data.  This version of the library supports
       only one	compression method (deflation) but  other  algorithms  may  be
       added later with	the same stream	interface.

       Compression  can	 be  done  in  a  single step if the buffers are large
       enough or can be	done by	repeated calls of  the	compression  function.
       In the latter case, the application must	provide	more input and/or con-
       sume the	output (providing more output space) before each call.

       The library also	supports reading and writing files  in	gzip(1)	 (.gz)
       format with an interface	similar	to that	of stdio.

       The  library  does  not install any signal handler.  The	decoder	checks
       the consistency of the compressed data, so  the	library	 should	 never
       crash even in the case of corrupted input.

       All  functions  of  the	compression library are	documented in the file
       zlib.h.	The distribution source	includes examples of use  of  the  li-
       brary in	the files test/example.c and test/minigzip.c, as well as other
       examples	in the examples/ directory.

       Changes to this version are documented in the file ChangeLog  that  ac-
       companies the source.

       zlib is built in	to many	languages and operating	systems, including but
       not limited to Java, Python, .NET, PHP, Perl, Ruby, Swift, and Go.

       An experimental package to read and write files	in  the	 .zip  format,
       written on top of zlib by Gilles	Vollant	(, is	avail-
       able at:  and	 also  in  the
	      contrib/minizip directory	of the main zlib source	distribution.

       The zlib	web site can be	found at:

       The  data  format used by the zlib library is described by RFC (Request
       for Comments) 1950 to 1952 in the files:  (for	the  zlib  header  and
	      trailer format)  (for	the deflate compressed
	      data format)  (for	the  gzip  header  and
	      trailer format)

       Mark Nelson wrote an article about zlib for the Jan. 1997 issue of  Dr.
       Dobb's Journal; a copy of the article is	available at:

       Before reporting	a problem, please check	the zlib web  site  to	verify
       that  you have the latest version of zlib; otherwise, obtain the	latest
       version and see if the problem still exists.  Please read the zlib  FAQ

       before	asking	 for   help.	Send   questions  and/or  comments  to, or (for the  Windows  DLL	 version)  to  Gilles  Vollant

       Version 1.2.11

       Copyright (C) 1995-2017 Jean-loup Gailly	and Mark Adler

       This  software is provided 'as-is', without any express or implied war-
       ranty.  In no event will	the authors be held  liable  for  any  damages
       arising from the	use of this software.

       Permission  is  granted to anyone to use	this software for any purpose,
       including commercial applications, and to alter it and redistribute  it
       freely, subject to the following	restrictions:

       1. The origin of	this software must not be misrepresented; you must not
	  claim	that you wrote the original software. If you use this software
	  in  a	 product, an acknowledgment in the product documentation would
	  be appreciated but is	not required.

       2. Altered source versions must be plainly marked as such, and must not
	  be misrepresented as being the original software.

       3. This	notice may not be removed or altered from any source distribu-

       Jean-loup Gailly	       Mark Adler

       The deflate format used by zlib was defined by Phil Katz.  The  deflate
       and  zlib  specifications  were written by L. Peter Deutsch.  Thanks to
       all the people who reported problems and	suggested various improvements
       in zlib;	who are	too numerous to	cite here.

       UNIX manual page	by R. P. C. Rodgers, U.S. National Library of Medicine

				  15 Jan 2017			       ZLIB(3)


Want to link to this manual page? Use this URL:

home | help