Apache HTTP Server

The Apache HTTP Server (commonly known as Apache httpd) is a free, open-source web server software that has been the most popular web server on the internet since April 1996, celebrating over 30 years of continuous development. Originally created by Robert McCool in 1995 and maintained by the Apache Software Foundation, Apache httpd has served as the foundation of the modern web, at its peak powering over 60% of all websites. As of 2026, it remains the second most used web server with approximately 25% market share. Apache's modular architecture is its defining feature: over 60 built-in modules extend functionality including mod_ssl (TLS/SSL encryption via OpenSSL), mod_rewrite (URL rewriting and redirection with regex-based rules), mod_proxy (reverse and forward proxying with load balancing across backend servers, supporting HTTP, AJP, FastCGI, and SCGI protocols), mod_deflate and mod_brotli (response compression), mod_cache (content caching with disk and memory backends), mod_security (web application firewall), mod_auth (authentication via Basic, Digest, LDAP, and database backends), mod_autoindex (automatic directory listings), mod_cgi and mod_cgid (CGI script execution), mod_php (embedded PHP interpreter), mod_wsgi (embedded Python WSGI applications), mod_jk (Apache JServ Protocol connector for Tomcat), mod_headers (HTTP header manipulation), mod_headers, mod_expires (cache control headers), mod_ratelimit (bandwidth throttling), and mod_macro (configuration templates). Apache supports MPMs (Multi-Processing Modules) including prefork (one process per connection), worker (hybrid process-thread), and event (asynchronous, default on most platforms). Configuration is via .htaccess files (directory-level) and httpd.conf (server-level).