Editing Apache HTTP Server (section)

==Feature overview==
Apache supports a variety of features, many implemented as [[Compiler|compiled]] [[Modular programming|modules]] which extend the core functionality. These can range from [[authentication]] schemes to supporting [[server-side]] programming languages such as <!-- ATTENTION AUTO-EDITORS, THESE UNDERSCORES ARE INTENTIONAL -->[[mod perl|Perl]], [[mod python|Python]], [[Tcl]] and [[PHP]]. Popular authentication modules include mod_access, mod_auth, mod_digest, and mod_auth_digest, the successor to mod_digest. A sample of other features include [[Transport Layer Security#SSL 1.0, 2.0, and 3.0|Secure Sockets Layer]] and [[Transport Layer Security]] support ([[mod_ssl]]), a [[proxy server|proxy]] module ([[mod_proxy]]), a [[URL rewriting]] module (mod_rewrite), custom log files (mod_log_config), and filtering support (mod_include and mod_ext_filter).

Popular compression methods on Apache include the external extension module, mod_gzip<!-- redirects to here -->, implemented to help with reduction of the size (weight) of web pages served over [[HTTP]]. [[ModSecurity]] is an open source intrusion detection and prevention engine for Web applications. 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 [[websites]]. For example, one computer with one Apache installation could simultaneously serve <code>example.com</code>, <code>example.org</code>, <code>test47.test-server.example.edu</code>, etc.

Apache features configurable error messages, [[Database management system|DBMS]]-based authentication databases, [[content negotiation]] and supports several [[graphical user interface]]s (GUIs).

It supports password authentication and [[digital certificate]] authentication. Because the source code is freely available, anyone can adapt the server for specific needs, and there is a large public library of Apache add-ons.<ref>{{cite web|url=https://www.webopedia.com/definitions/apache-web-server/|title=Apache Web Server|work=webopedia.com|date=23 March 1998|access-date=12 May 2021|archive-date=12 May 2021|archive-url=https://web.archive.org/web/20210512193103/https://www.webopedia.com/definitions/apache-web-server/|url-status=live}}</ref>

A more detailed list of features is provided below:
* Loadable Dynamic Modules
* Multiple Request Processing modes (MPMs) including [[Event driven programming|Event-based/Async]], Threaded and Prefork.
* Highly scalable (easily handles [[c10k problem|more than 10,000 simultaneous connections]])
* Handling of static files, index files, auto-indexing and content negotiation
* <kbd>.htaccess</kbd> per-directory configuration support<ref>{{cite web | url = https://httpd.apache.org/docs/2.4/howto/htaccess.html | title = Apache HTTP Server Tutorial: .htaccess files | publisher = Apache.org | access-date = 2016-02-19 | archive-date = 2016-02-25 | archive-url = https://web.archive.org/web/20160225155611/http://httpd.apache.org/docs/2.4/howto/htaccess.html | url-status = live }}</ref>
* [[Reverse proxy]] with caching<ref>{{cite web | url = https://httpd.apache.org/docs/2.4/mod/mod_proxy.html | title = mod_proxy | publisher = Apache.org | access-date = 2016-02-19 | archive-date = 2018-07-29 | archive-url = https://web.archive.org/web/20180729204047/http://httpd.apache.org/docs/2.4/mod/mod_proxy.html | url-status = live }}</ref>
** [[Load balancing (computing)|Load balancing]]<ref>{{cite web | url = https://httpd.apache.org/docs/2.4/mod/mod_proxy_balancer.html | title = mod_proxy_balancer | publisher = Apache.org | access-date = 2016-02-19 | archive-date = 2016-02-13 | archive-url = https://web.archive.org/web/20160213163641/http://httpd.apache.org/docs/2.4/mod/mod_proxy_balancer.html | url-status = live }}</ref> with in-band health checks
** Multiple load balancing mechanisms
** [[Fault-tolerant design|Fault tolerance]] and Failover with automatic recovery
** [[WebSocket]], [[FastCGI]], [[Simple Common Gateway Interface|SCGI]], [[Apache JServ Protocol|AJP]] and [[uWSGI]] support with caching
** Dynamic configuration<ref>{{cite web|url=https://httpd.apache.org/docs/trunk/howto/reverse_proxy.html#manager|title=Balancer Manager|publisher=Apache.org|access-date=2016-02-19|archive-date=2016-03-04|archive-url=https://web.archive.org/web/20160304103556/https://httpd.apache.org/docs/trunk/howto/reverse_proxy.html#manager|url-status=live}}</ref>
* [[Transport Layer Security|TLS/SSL]] with [[Server Name Indication|SNI]] and [[OCSP stapling]] support, via [[OpenSSL]] or [[wolfSSL]].
* Name- and IP address-based virtual servers
* [[IPv6]]-compatible
* [[HTTP/2]] support
* Fine-grained authentication and authorization access control<ref>{{cite web|url=https://httpd.apache.org/docs/2.4/howto/auth.html|title=Authentication and Authorization|publisher=Apache.org|access-date=2016-02-19|archive-date=2018-01-31|archive-url=https://web.archive.org/web/20180131130634/http://httpd.apache.org/docs/2.4/howto/auth.html|url-status=live}}</ref>
* [[gzip]] compression and decompression
* URL rewriting<ref>{{cite web | url = https://httpd.apache.org/docs/2.4/mod/mod_rewrite.html | title = mod_rewrite | publisher = Apache.org | access-date = 2016-02-19 | archive-date = 2016-02-13 | archive-url = https://web.archive.org/web/20160213152803/http://httpd.apache.org/docs/2.4/mod/mod_rewrite.html | url-status = live }}</ref>
* Headers<ref>{{cite web | url =  https://httpd.apache.org/docs/2.4/mod/mod_headers.html | title =  mod_headers | publisher =  Apache.org | access-date =  2016-02-19 | archive-date =  2016-02-21 | archive-url =  https://web.archive.org/web/20160221033800/http://httpd.apache.org/docs/2.4/mod/mod_headers.html | url-status =  live }}</ref> and content<ref>{{cite web | url = https://httpd.apache.org/docs/2.4/mod/mod_sed.html | title = mod_sed | publisher = Apache.org | access-date = 2016-02-19 | archive-date = 2016-03-04 | archive-url = https://web.archive.org/web/20160304013210/https://httpd.apache.org/docs/2.4/mod/mod_sed.html | url-status = live }}</ref><ref>{{cite web | url = https://httpd.apache.org/docs/2.4/mod/mod_substitute.html | title = mod_substitute | publisher = Apache.org | access-date = 2016-02-19 | archive-date = 2016-03-04 | archive-url = https://web.archive.org/web/20160304073406/http://httpd.apache.org/docs/2.4/mod/mod_substitute.html | url-status = live }}</ref> rewriting
* Custom logging with rotation
* Concurrent connection limiting
* Request processing rate limiting
* [[Bandwidth throttling]]
* [[Server Side Includes]]<ref>{{cite web | url = https://httpd.apache.org/docs/2.4/howto/ssi.html | title = Apache httpd Tutorial: Introduction to Server Side Includes | publisher = Apache.org | access-date = 2016-02-19 | archive-date = 2016-02-18 | archive-url = https://web.archive.org/web/20160218133535/http://httpd.apache.org/docs/2.4/howto/ssi.html | url-status = live }}</ref>
* [[IP address]]-based [[geolocation]]
* User and Session tracking<ref>{{cite web | url = https://httpd.apache.org/docs/2.4/mod/mod_usertrack.html | title = mod_usertrack | publisher = Apache.org | access-date = 2021-05-12 | archive-date = 2021-05-12 | archive-url = https://web.archive.org/web/20210512192558/http://httpd.apache.org/docs/2.4/mod/mod_usertrack.html | url-status = live }}</ref>
* [[WebDAV]]
* Embedded [[Perl]], [[PHP]] and [[Lua (programming language)|Lua]] scripting
* [[Common Gateway Interface|CGI]] support<ref>{{cite web | url = https://httpd.apache.org/docs/2.4/howto/cgi.html | title = Apache Tutorial: Dynamic Content with CGI | publisher = Apache.org | access-date = 2016-02-19 | archive-date = 2021-11-15 | archive-url = https://web.archive.org/web/20211115181448/https://httpd.apache.org/docs/2.4/howto/cgi.html | url-status = live }}</ref>
* <code>public_html</code> per-user web-pages<ref>{{cite web | url = https://httpd.apache.org/docs/2.4/howto/public_html.html | title = Per-user web directories | publisher = Apache.org | access-date = 2016-02-19 | archive-date = 2016-02-16 | archive-url = https://web.archive.org/web/20160216122731/http://httpd.apache.org/docs/2.4/howto/public_html.html | url-status = live }}</ref>
* Generic expression parser<ref>{{cite web| url = https://httpd.apache.org/docs/2.4/expr.html| title = Expressions in Apache HTTP Server| publisher = Apache.org| access-date = 2016-02-19| archive-date = 2016-02-29| archive-url = https://web.archive.org/web/20160229120307/http://httpd.apache.org/docs/2.4/expr.html| url-status = live}}</ref>
* Real-time status views<ref>{{cite web | url = https://httpd.apache.org/docs/2.4/mod/mod_status.html | title = mod_status | publisher = Apache.org | access-date = 2016-02-19 | archive-date = 2016-02-13 | archive-url = https://web.archive.org/web/20160213154107/http://httpd.apache.org/docs/2.4/mod/mod_status.html | url-status = live }}</ref>
* [[FTP]] support (by a separate module)<ref>{{cite web | url= https://httpd.apache.org/mod_ftp/mod/mod_ftp.html | title= Apache Module: mod_ftp | publisher= Apache.org | access-date= 2017-07-08 | archive-date= 2017-07-10 | archive-url= https://web.archive.org/web/20170710072314/http://httpd.apache.org/mod_ftp/mod/mod_ftp.html | url-status= live }}</ref>