Query fan-out is one of the few AI search mechanisms Google has described in its own documentation, which makes it unusual. Most of what gets written about how AI search works is inference. This part is not.
Google’s AI features documentation states that both AI Overviews and AI Mode may use a “query fan-out” technique, issuing multiple related searches across subtopics and data sources to develop a response.
Google said it earlier and more plainly in the AI Mode launch post on 20 May 2025:
“AI Mode uses our query fan-out technique, breaking down your question into subtopics and issuing a multitude of queries simultaneously on your behalf.”
That is the whole confirmed mechanism, from two Google sources. One question in, many searches run, one answer synthesised from what comes back.
What it actually changes
The shift is from ranking for a query to being present across a topic.
Under classic search, a page competes for a query. Ten blue links, you are in them or you are not. Under fan-out, the system runs searches you never see for subtopics you did not target, and assembles an answer from whatever surfaces across all of them. Your page can contribute to an answer for a question it does not rank for, because it was the best result for one of the sub-searches.
Google also notes that during this process its models identify supporting web pages, which lets it display a wider and more diverse set of links than a standard results page would. More slots, drawn from more searches.
The practical consequence is unglamorous. Thin coverage of a topic gives the system one narrow way to reach you. Thorough coverage, where the adjacent questions are actually answered somewhere on your site, gives it many. That is not a new technique. It is the old argument for topical depth, with a clearer mechanism behind it.
What Google says you should do about it
Nothing special, in Google’s own words.
The same documentation that confirms fan-out also says there are no additional requirements to appear in AI Overviews or AI Mode, and no other special optimisations necessary. The guidance is the ordinary set: make sure your pages can be crawled, write genuinely helpful content, keep page experience decent.
This is worth sitting with, because a large amount of writing about query fan-out proposes a technical response to it. Restructure for sub-queries. Write to a fan-out template. Buy a tool that predicts the fan-out set. Google’s position is that the mechanism exists and that no new optimisation follows from it.
You can reasonably believe Google is understating things. Vendors have an interest in the opposite claim, and Google has an interest in fewer people gaming it. But if someone sells you a fan-out optimisation method, the burden is on them to show it beats doing the normal thing well, and that evidence is not currently public.
The numbers nobody can source
You will see specific claims about how many sub-queries a fan-out generates. Dozens. Hundreds. A precise average.
Google has not published a figure. Every number in circulation is an estimate, an inference from observed behaviour, or a repetition of someone else’s estimate. Some may be roughly right. None is disclosed, and none should be quoted as though it were.
The same applies to claims that fan-out surfaces content that would otherwise sit on page three. It is a plausible reading of “a wider and more diverse set of links”, and it is not something Google has stated.
Which crawler this depends on
Googlebot, and only Googlebot.
Google states that robots.txt directives for Googlebot control crawling for Search, and that this applies to AI features as well. There is no separate AI Mode fetcher to allow.
That matters for two reasons. First, if you have blocked Googlebot from a section, that section is out of AI Mode too. Second, Googlebot is one of the very few crawlers that documents JavaScript rendering, so content behind client-side rendering is in a better position here than it is with most AI crawlers. Better, not safe: Google queues pages for rendering and says a page may sit in that queue longer than a few seconds.
What the effect looks like from outside
You cannot see the sub-queries, but you can see their consequence.
Ahrefs compared AI Mode and AI Overviews in a December 2025 study by Despina Gavoyannis, using September 2025 US data from Brand Radar. Note the two samples: 540,000 query pairs for the citation analysis and 730,000 for content similarity.
- Citation overlap on the same queries was 13.7%, rising to 16.3% for top citations only.
- Semantic similarity between the two answers was 86%.
- AI Mode responses were roughly 4x longer and named 3.3 entities on average against 1.3.
- Word-level overlap was 16%, with an identical first sentence just 2.51% of the time.
Two systems reaching nearly the same conclusion while citing almost entirely different pages is what an expanded retrieval layer looks like from the outside. The destination is stable, the path is not. That also means an AI Overviews strategy does not automatically carry into AI Mode.
The usual limits apply. One vendor’s dataset, one month, one market, measured with that vendor’s own product. Best available, still a single study.
You cannot measure it in Search Console
Worth knowing before you plan around any of this.
Google’s documentation says sites appearing in AI features “are included in the overall search traffic in Search Console”, reported under the Web search type. There is no AI Mode breakout: no filter, no separate row, no dimension.
AI Mode impressions and clicks are therefore already mixed into your organic numbers and cannot be separated from them. You cannot A/B a fan-out strategy against a normal one using Google’s own reporting, because that reporting does not distinguish them. Anyone quoting you an AI Mode traffic figure from Search Console is deriving it, not reading it.
What to do
Cover the topic, not the keyword. If fan-out searches subtopics, the win condition is having genuinely useful pages across those subtopics. This is the same advice as before, with a mechanism attached.
Answer the question near the top. Synthesis favours content where the answer is extractable without inference. Burying the answer in paragraph nine is worse than it used to be.
Check Googlebot can reach and render everything. Fan-out cannot surface what was never indexed.
Ignore anyone selling you a fan-out score. Google says no special optimisation is required. Until someone publishes evidence to the contrary, that is the most authoritative statement available and it is free.
The short version
Query fan-out is real, documented by Google, and it means one question triggers many searches. What follows from it is broader topical coverage and clear answers, not a new technical discipline. The specific sub-query counts you see quoted are unsourced, and Google’s own guidance is that nothing special is required.