Remove WWW prefix from your website

Question

How does Stack Overflow (and other web sites) remove the \'www\' prefix when it\'s entered as part of a URL?

Is it a redirect, a rewrite or something else entirely?<

Answer 1

On Apache, it looks like this (inside an .htaccess file):

RewriteEngine On
RewriteCond %{HTTP_HOST} ^www.example.com$ [NC]
RewriteRule ^(.*)$ http://example.com/$1 [R=301,L]