Apache

Apache, formally the Apache HTTP Server (daemon name httpd), is an open-source web server developed by the Apache Software Foundation since 1995. It listens for HTTP and HTTPS requests and returns responses — static files, output from PHP or other application backends, redirects and error pages. For roughly two decades it was the most widely deployed web server on the internet, and it still powers a large share of shared hosting environments today.

How Apache works

Apache's architecture is modular: a compact core is extended with loadable modules such as mod_rewrite for URL rewriting, mod_ssl for TLS, mod_headers, mod_proxy and the ModSecurity web application firewall. Request handling is governed by a Multi-Processing Module (MPM): prefork spawns a separate process per connection (required by the embedded mod_php), while worker and the modern event MPM use threads and handle keep-alive connections far more efficiently, typically paired with PHP-FPM over FastCGI.

Apache's signature feature is the .htaccess file: a per-directory configuration override that lets site owners define redirects, access rules or custom headers without touching the main server config and without a service restart.

Practical application

Apache is the default engine behind most hosting control panels — cPanel, DirectAdmin, Plesk — largely because .htaccess gives every customer safe, sandboxed control over their own site's behavior. Popular PHP applications like WordPress and PrestaShop ship ready-made mod_rewrite rules, so pretty URLs work out of the box on a typical shared hosting account.

In higher-traffic architectures Apache frequently sits behind Nginx acting as a reverse proxy: the event-driven front end terminates thousands of concurrent connections and serves static assets, while Apache processes the dynamic requests it is best at. Choosing between them comes down to priorities — per-directory flexibility and ecosystem maturity on one side, raw concurrency and a smaller memory footprint on the other.