Keeping Google’s Affiliate Auction policy in mind is usually a good idea for anybody who manages more than one account on Google Ads. The Google Ads Affiliate Policy effectively states that Google will display only one advert per top-level domain.
This means that, if you’re an affiliate advertiser, your ads won’t display if some other affiliate or website is running ads with display URL’s that point to the same domain.
Top Level Domains
The top level domain is the highest level of domain hierarchy. A top level domain would, for example, be www.something.com.
Essentially, this means that if you have two ads with the same display URL, only one of them can be triggered for any given search.
Google gives the following examples of URL’s that would be considered as pointing to the same top-level domain:
The following examples are given for URL’s that would be seen as different from each other:
In other words, domains with different extensions are considered unique in the same way that domains with entirely different URL’s, (like example.com and test.com) would be considered unique.
We’re not sure how this affects sub-domains, but we’ve asked Google, and will update this as soon as we get a reply.
Mirrored Sites & Landing Pages
Google also won’t show multiple ads for identical (or similar) landing pages, even if they’re on different domains.
If another advertiser’s ad points to a page that is similar or identical to yours, then the advert with the highest Ad Rank will be displayed.