If I search under "site:www.example.com" I don't see any results, but if I search "site:example.com" I do. Why?

Question

In Search Console I have it as "don't set preferred domain."

What could be causing this?

Answer 1

You should check your HTTP headers. If www.example.com gives 404 not found error, Google will not index that subdomain.

To make sure you have both version idexed and also avoiding duplication of content, try to add this to your .htaccess:

RewriteEngine on
# Redirect non-www to wwww
RewriteCond %{HTTP_HOST} !^www\.yourdomain\.org [NC]
RewriteRule ^(.*)$ http://www.yourdomain.org/$1 [R=301,L]