Learn to redirect www to non-www URLs or non www to www URLs using .htaccess file. You can do 301 permanent redirect on shared server with multiple domains also. If you have a self hosted WordPress website, you it would be useful for you.
mod_rewrite module of Apache server
Apache server uses modules for various functionalists. mod_rewrite is a module that enables redirection and URL rewriting. If this module is installed and available on Apache server, only then your redirection will work.
If mod_rewrite is available, it will take your redirection commands from .htaccess file.
Redirect old domain to new domain
<IfModule mod_rewrite.c> RewriteEngine on RewriteCond %{HTTP_HOST} ^www.olddomainname.com$ [OR] RewriteCond %{HTTP_HOST} ^olddomainname.com$ RewriteRule ^(.*)$ http://www.newdomainname.com/$1 [R=301,L] </IfModule>
Redirect www to non-www URL Domain
<IfModule mod_rewrite.c> RewriteEngine On RewriteCond %{HTTP_HOST} ^www.example.com [NC] RewriteRule ^(.*) http://example.com/$1 [L,R=301] </IfModule>
Redirect non-www to www URL Domain
<IfModule mod_rewrite.c> RewriteEngine On RewriteCond %{HTTP_HOST} ^example.com [nocase] RewriteRule ^(.*) http://www.example.com/$1 [last,redirect=301] </IfModule>