The Apache HTTP Server, commonly referred to simply as Apache [əˈpætʃi], is a web server notable for playing a key role in the initial growth of the World Wide Web. Apache was the first viable alternative to the Netscape Communications Corporation web server (currently known as Sun Java System Web Server), and has since evolved to rival other Unix-based web servers in terms of functionality and performance.
Apache is developed and maintained by an open community of developers under the auspices of the Apache Software Foundation. The application is available for a wide variety of operating systems, including Unix, FreeBSD, Linux, Solaris, Novell NetWare, Mac OS X, Microsoft Windows, OS/2, TPF, and eComStation. Released under the Apache License, Apache is characterized as free software and open source software.
There have been two explanations of the project's name. According to the Apache Foundation, the name was chosen out of respect for the Native American Indian tribe of Apache (Indé), well-known for their endurance and their skills in warfare. However, the original FAQ on the Apache Server project's website, from 1996 to 2001, claimed that "The result after combining [the NCSA httpd patches] was A PAtCHy server. The first explanation was supported at an Apache Conference and in an interview in 2000 by Brian Behlendorf, who said that the name connoted "Take no prisoners. Be kind of aggressive and kick some ass. Behlendorf then contradicted this in a 2007 interview, stating that "The Apache server isn't named in honor of Geronimo's tribe" but that so many revisions were sent in that "the group called it 'a patchy Web server'. Both explanations are probably appropriate though the pun explanation has fallen into disfavor.
Version 2 of the Apache server was a substantial re-write of much of the Apache 1.x code, with a strong focus on further modularization and the development of a portability layer, the Apache Portable Runtime. The Apache 2.x core has several major enhancements over Apache 1.x. These include UNIX threading, better support for non-Unix platforms (such as Microsoft Windows), a new Apache API, and IPv6 support. The first alpha release of Apache 2 was in March 2000, with the first general availability release on 6 April 2002.
Version 2.2 introduced a more flexible authorization API. It also features improved cache modules and proxy modules.
Popular compression methods on Apache include the external extension module, mod_gzip, implemented to help with reduction of the size (weight) of web pages served over . Apache logs can be analyzed through a web browser using free scripts such as AWStats/W3Perl or Visitors.
Virtual hosting allows one Apache installation to serve many different actual websites. For example, one machine, with one Apache installation could simultaneously serve www.example.com, www.test.com, test47.test-server.test.com, etc.
Apache features configurable error messages, DBMS-based authentication databases, and content negotiation. It is also supported by several graphical user interfaces (GUIs) which permit easier, more intuitive configuration of the server.
Apache is redistributed as part of various proprietary software packages including the Oracle Database or the IBM WebSphere application server. Mac OS X integrates Apache as its built-in web server and as support for its WebObjects application server. It is also supported in some way by Borland in the Kylix and Delphi development tools. Apache is included with Novell NetWare 6.5, where it is the default web server.
Apache is used for many other tasks where content needs to be made available in a secure and reliable way. One example is sharing files from a personal computer over the Internet. A user who has Apache installed on their desktop can put arbitrary files in the Apache's document root which can then be shared.
Programmers developing web applications often use a locally installed version of Apache in order to preview and test code as it is being developed.
Microsoft Internet Information Services (IIS) is the main competitor to Apache, trailed by Sun Microsystems' Sun Java System Web Server and a host of other applications such as Zeus Web Server. Some of the biggest web sites in the world are run using Apache. Google's search engine front end is based on a modified version of Apache, named Google Web Server (GWS). Several Wikimedia projects also run on Apache servers .
The software license under which software from the Apache Foundation is distributed is a distinctive part of the Apache HTTP Server's history and presence in the open source software community. The Apache License allows for the distribution of both open and closed source derivations of the source code.
The Free Software Foundation does not consider the Apache License to be compatible with version 2 of the GNU General Public License (GPL) in that software licensed under the Apache License cannot be integrated with software that is distributed under the GPL:
However, version 3 of the GPL includes a provision (Section 7e) which allows it to be compatible with licenses that have patent retaliation clauses, including the Apache License.
The name Apache is a registered trademark and may only be used with the trademark holder's express permission.