Site diversity

Google introduced this system in June 2019 to stop one website from filling an entire results page. Before it, a strong domain could hold four, five, or more of the top ten spots for a single query. Now, for most searches, you see at most two listings from any one site.

What decides the two slots

• Exceptions. Google may show more than two listings “where our systems determine it’s especially relevant,” which usually means branded or navigational queries where people clearly want that one site.
• Subdomains. blog.example.com and example.com normally count as the same site, so a subdomain does not buy you an extra slot. Google reserves the right to treat a subdomain as separate when its systems deem it relevant to do so.
• Scope. The cap applies to standard web results, not features like Top Stories, image packs, or video carousels.

Danny Sullivan framed this as a display change, not a ranking one: pages that ranked well still rank well, Google just shows fewer of them from the same source. The practical effect is the same for you. If three of your pages target one keyword, only your two strongest normally appear, and the third is effectively invisible for that query. That makes near-duplicate pages competing on the same term a liability rather than extra coverage.