htaccess Redirecting non-www to www with .htaccess

If you want to redirect all non-www requests to your site to the www version, all you need to do is add the following code to your .htaccess file:
in your .htaccess file

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

This will redirect any requests to http://my-domain.com to http://www.my-domain.com. There are several benefits from doing that:

* It will avoid duplicate content in Google
* It will avoid the possibility of split page rank and/or split link popularity (inbound links).
* It’s nicer, and more consistent.

Note that if your site has already been indexed by Google without the www, this might cause unwanted side effects, like lost of PR. I don’t think this would happen, or in any case it would be a temporary issue (we are doing a permanent redirect, 301, so Google should transfer all rankings to the www version). But anyway, use at your own risk!

Something nice about the code above is that you can use it for any website, since it doesn’t include the actual domain name.
Redirecting www to non-www

If you want to do the opposite, the code is very similar:
in your .htaccess file

RewriteEngine On
RewriteCond %{HTTP_HOST} !^my-domain\.com$ [NC]
RewriteRule ^(.*)$ http://my-domain.com/$1 [R=301,L]

In this case we are explicitly typing the domain name. I’m sure it’s possible to do it in a generic way, but I haven’t had the time to work one out and test it. So remember to change ‘my-domain’ with your domain name!

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

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