In web hosting, "Apache" almost always means the Apache HTTP Server, free open-source software that delivers websites to browsers. It first appeared in 1995, is maintained by the Apache Software Foundation, and still runs a large share of the web, especially on shared hosting plans.
The name is also used for the foundation itself, which looks after many unrelated projects such as Kafka and Spark. If someone mentions Apache alongside hosting or .htaccess, they mean the web server.
How Apache is put together
Apache has a small core and a large set of modules you switch on as needed: mod_ssl for HTTPS, mod_rewrite for URL rules, mod_headers for response headers and many more. How it handles connections is chosen through a multi-processing module. The older prefork model uses one process per connection, which is simple but memory-hungry; the event model behaves more like Nginx and handles idle connections far more cheaply.
The .htaccess file
Apache's best-known feature is the .htaccess file. Drop one into any folder and its rules apply to that folder and everything under it, without touching the main server configuration or restarting anything. That is why shared hosts favour Apache: customers can set redirects, password-protect a folder or force HTTPS without server access. The cost is speed, because Apache checks for these files on requests.
Example: fixing old links after a redesign
A dental practice moves its page from /services.html to /treatments/. On an Apache shared host, the owner or developer adds one line to .htaccess in the site's root folder: Redirect 301 /services.html /treatments/. Visitors and search engines following the old address are sent to the new one straight away.
When you will run into Apache
Mostly on cPanel-style hosting and older WordPress installs, where WordPress writes its own rewrite rules into .htaccess for pretty URLs. If you build on a modern platform or a static host, you will probably never see it.
Common Apache mistakes
- A broken .htaccess line. A single typo causes a 500 Internal Server Error for the whole folder. Keep a copy before editing.
- Redirect loops when forcing HTTPS. Behind a proxy or CDN, the server may not see that the request was already secure, and keeps redirecting.
- Using prefork on a busy site. Memory runs out long before the CPU is busy.
- Copying rules meant for Nginx. The two servers use completely different configuration syntax.
Related terms
- Web server: what Apache is.
- Nginx: the main alternative, with central config only.
- Shared hosting: where Apache is most common.
- HTTPS: enabled in Apache through mod_ssl.