How does pointing a domain via a CNAME record affect the SEO?

Question

We are contemplating pointed secondary domains to a primary domain via CName records to keep things simple for our customers but we are concerned that this will negatively affect SEO.

How does pointing a domain via a CNAME record affect the SEO of the primary site (the one the domain is being redirected to)? Does Google see the domain with the CName as another site? And if so, would it penalize both sites for having duplicate content?

I read somewhere, that domains redirected via CNAme are treated as a 301 redirect. But if the primary domain is accessible, how would Google handle this since there is no redirect to the domain with the CName when accessing the primary domain?

Thanks for your help.

Answer 1

Two domains pointing to the same site is not the same as a 301 redirect and will cause duplicate content issues. You either need to do a 301 redirect once the user reaches one of the addon domains or use canonical URLs to tell Google which URL is the one it should consider the primary URL and to use in their search results.