Remove sub-domains from a URL
It's not possible to change a site URL to a URL without a sub-domain (also referenced to as a 'naked domain'). Using the domain example.com, a URL with a sub-domain would be http://www.example.com; the naked domain is http://example.com.
We recommend you redirect the naked domain to a sub-domain like http://www.example.com. Learn more about URL redirects.