apache redirect from non www to www

Question

I have a website that doesn\'t seem to redirect from non-www to www.

My Apache configuration is as follows:

RewriteEngine On
### re-direct t         


        

Answer 1

This works for me:

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

I use the look-ahead pattern (?!www.domain.com) to exclude the www subdomain when redirecting all domains to the www subdomain in order to avoid an infinite redirect loop in Apache.