What is Apache (web server)?
Apache HTTP Server is a free, open-source web server software that receives requests from web browsers and delivers web pages and other content in response. Developed and maintained by the Apache Software Foundation, it has been one of the most widely deployed web servers on the internet since its initial release in 1995.
When a visitor types a URL into their browser, a web server is the program responsible for receiving that request and sending back the appropriate files, whether HTML pages, images, stylesheets, or scripts. Apache performs this role by listening for incoming HTTP and HTTPS requests and fulfilling them according to a set of configurable rules. It runs on the server, entirely invisible to end users, yet it is fundamental to how nearly every website functions.
Apache is particularly well known for its modular architecture. Functionality is extended through modules, which are components that can be enabled or disabled depending on the needs of a given server. Common modules handle tasks such as URL rewriting, authentication, compression, and SSL encryption. The mod_rewrite module, for example, is widely used in SEO to create clean, human-readable URLs and to set up redirects, making it a familiar tool for both developers and SEO professionals.
Configuration in Apache is managed primarily through a file called httpd.conf, as well as through .htaccess files. The .htaccess file is a directory-level configuration file that allows server behavior to be modified on a per-folder basis without requiring access to the main server configuration. This makes it especially practical for shared hosting environments, where individual site owners can control redirects, access restrictions, and caching rules without server administrator privileges.
Apache operates on a process-based or thread-based model, depending on the Multi-Processing Module (MPM) selected. For many years, the prefork MPM was the standard, spawning a new process for each connection. More recent configurations use the event MPM, which handles connections more efficiently and is better suited to high-traffic environments.
In terms of market position, Apache competes primarily with Nginx, another open-source web server that takes a different, event-driven approach to handling connections. While Nginx has gained significant ground, particularly for serving static content at scale, Apache remains dominant across shared hosting platforms and is a foundational component of the classic LAMP stack (Linux, Apache, MySQL, PHP).
For developers and SEO professionals, understanding Apache is practically relevant because server-level configuration directly affects site performance, URL structure, redirect handling, and security headers, all of which influence both user experience and search engine crawling.