: Canonical URLs with multiple domains Within my CMS I can add multiple domains. IE: domain-1.com and domain-2.com. The way my CMS is setup I can access the same content across both domains. For

@Tiffany637

The first question might be why do you have two duplicate sites? Is there a particular reason? If there is no reason then I would suggest not to have duplicate domains, but if you must, then yes you can use cross domain canonical tag to avoid duplicate content issues in Google.

However, its seems that you may be a bit confused about cross domain canonical tags. To use cross domain canonical tags you have to chose one website that is the 'canonical' site that you want to be the main site that will rank in Google. The other site is the duplicate site and if using cross domain canonical tags will eventually be de-indexed in Google.

To use cross domain canonical tags, one of the canonical tags must reference the other website.

e.g

Main site www.domain-1.org/page-1
Could have a self referencing canonical tag:

<link rel="canonical" href="http://www.domain-1.org/page-1" />


Then the duplciate site www.domain-2.org/page-2
Would have a canonical tag referencing the main site:

<link rel="canonical" href="http://www.domain-1.org/page-1" />


More info from Google on Canonical tags here About rel="canonical"

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@Tiffany637

How ever your CMS works on this case is not a big deal, but each domain is different site (except sub domain) So the duplicate content is an issue within your one domain.

In your case the domain-1 's page repeated in domain-2 so its not a duplicate content in domain-1 or domain-2 . Only the bad impact on this case is, exact same content available on two sites(different domain) that have some bad impression in Search Engines.

Google Says




There are situations where it's not easily possible to set up
redirects. This could be the case when you need to migrate to a new
domain name using a web server that cannot create server-side
redirects. In this case, you can use the rel="canonical" link element
to specify the exact URL of the domain preferred for indexing. While
the rel="canonical" link element is seen as a hint and not an absolute
directive, we do try to follow it where possible.




I think there is no role for robot.txt or sitemap.xml in this case.

For more reading.

In your case the same content on both site is not ignorable, try to consider domain as Primary and another one as Secondary (boost any of the one website as main in ranking) and other one can point a canonical URL to the main domain.

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