Query fan-out — Google’s own term for breaking one question into many simultaneous searches and assembling the answer from all of them.
In Google’s own words
“AI Mode uses our query fan-out technique, breaking down your question into subtopics and issuing a multitude of queries simultaneously on your behalf.” For the Deep Search variant, Google says it “can issue hundreds of searches, reason across disparate pieces of information, and create an expert-level fully-cited report in just minutes.”
Source: Google, May 2025.
What it means for you
“Best physical therapist in Lincoln Park” does not stay one query. It becomes questions about credentials, insurance, reviews, specialties and hours — each fetching its own set of sources. Pages that would never have surfaced for the original phrase get pulled in through a branch of the fan-out.
This is the mechanism behind the most counter-intuitive number in AI search: only 38% of pages cited in AI Overviews ranked in the top ten for the query.
The practical consequence
Optimising a page for one head term optimises it for one branch. Coverage of the surrounding questions is what gets you into the other branches — which is why a thin page targeting a fat keyword now performs worse than a thorough page that answers the whole neighbourhood of questions around it.
Related: Google AI Mode, AI Overviews, GEO.