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Query fan-outs (QFOs, also written fanouts or query expansion) are the extra searches an AI engine runs behind the scenes to answer one prompt. Peec’s analysis of 5 million fan-outs (full study, May 2026) explains the mechanism: a prompt like “best headphones” fans out into hidden sub-queries — best wireless headphones, best noise-cancelling for flights, best budget options, current-year variants — and the engine merges all results into one answer. Why fan-outs matter for GEO: ChatGPT uses Reciprocal Rank Fusion (RRF), an algorithm that combines scores across the sub-queries. Content that appears across multiple fan-out searches scores higher than content that only surfaces for one — so ranking in AI search means being present across dozens of related queries, not winning one keyword. The structure, length, and number of QFOs directly determine which sources get retrieved and ultimately cited. Key facts from Peec’s 2026 fan-out research, each with its own page: Source: Patterns we see in ChatGPT query fanouts, Peec (Tomek Rudzki), May 2026.