Not linked domains appear in Google Serps

[albert0346]

Hello,

I got a couple new domains in addition to my old one. All domains point to the same address, i.e. use the same content. Right now only the old domain has links to it. The new domains are not registered at Google. When I search now in Google for the new domain names all appear in the Serps. How does Google know about those new domains when there is no link to them and they are not registered?

Thanks in advance for your answer.

Albert

[tedster]

Google has many ways to learn about domain names, including the fact that they are formally a registrar and can access WHOIS data en masse.

Pointing several domains to the same content can bring you trouble eventually. The best practice (short of developing each domain with unique content) is to 301 redirect all but one domain to the domain name that you choose as the principal one. Other methods of "domain forwarding" have been known to create troubles.