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What is query fan-out and why it matters in LLM search?

Understand how a single prompt expands into multiple internal queries.

Apolline Vanneste avatar
Written by Apolline Vanneste
Updated this week

When interacting with an LLM, users enter a single prompt and receive a single answer. However, this answer is rarely built from one question alone.

Behind the scenes, LLMs like ChatGPT, Gemini or Claude often expand a prompt into multiple internal queries to retrieve information, compare viewpoints and structure their response. This mechanism is called query fan-out.

Query Fan-out provides a clearer lens to understand:

  • how presence is distributed across multiple sub-questions

  • how influence and visibility emerge across LLM answers

  • how indirect traffic and brand exposure can be generated


1. Definition: What is Query Fan-out?

Term

What It Means

Key Attributes

Query Fan-out

The process by which an LLM expands a single user prompt into multiple internal queries to generate its answer.

- Happens internally in the model
- Not visible to users
- Varies by engine, version and over time

In practice, the model does not answer one question.
It answers several related questions, then synthesizes them into a single response.

Example

User prompt:

“What is the best project management software for small teams?”

To answer this, the model may internally explore queries such as:

  • What tools are commonly used by small teams?

  • Which features matter most?

  • How do popular solutions compare?

  • What are their main strengths and limitations?

Each internal query contributes a piece of information used to assemble the final answer.


2. Query Fan-out, Intent and Answer Construction

Query fan-out is closely linked to how the model interprets what the user is trying to achieve.

Rather than treating a prompt as a single request, the LLM:

  • breaks it down into several angles

  • explores each angle through an internal query

  • combines these perspectives into one answer

In practice, fan-out queries often cover:

  • explanation or definition

  • comparison between options

  • examples or recommendations

This is how LLMs translate intent into smaller, answerable questions and assemble a complete response.


3. What We Observe in Practice (based on internal tests)

The following observations are based on internal experiments conducted by our data science team and reflect current behaviours.

  • A single prompt can generate from zero up to 15–20 fan-out queries, depending on the model and its version. Some prompts may trigger little to no fan-out, especially when the question is very narrow or requires limited exploration.

  • Fan-out is not fixed over time: the same prompt can produce different internal queries at different moments. This helps explain why LLM answers are not always perfectly stable, even when the prompt does not change

  • Being ranked on Google for fan-out queries does not directly increase the probability of appearing as a Source or a Link in LLM answers

  • Some models expose, via their APIs, the URLs associated with fan-out queries

  • Being present in these URLs increases the likelihood of later appearing in the final answer (as a Source or a Link)

  • The relative position compared to competitors appears more important than absolute ordering

These signals should be read as interpretation cues, not deterministic rules.


To Recap

  • Query fan-out describes how a single prompt expands into multiple internal queries

  • These queries explore different angles of the same question

  • Fan-out varies by engine, version and over time

  • It plays a key role in how sources, links and brands appear in LLM answers


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