What is retrieval in AI search?
Retrieval is the step where the system locates and selects the sources that will support the answer, before writing a single word. It is the architecture known as RAG, short for retrieval-augmented generation. For anyone who wants to be cited, this is the step that matters: what is not retrieved cannot be cited, however good it is.
What happens inside retrieval
The system reformulates the user’s question, usually breaking it into several sub-searches (query fan-out), queries an index, its own or a partner search engine’s, and pulls back a set of candidate documents. Those candidates are then re-ranked, weighing fit to the retrieved passage, source trustworthiness, freshness and how cleanly the content extracts.
Only then does the model write. The answer is composed from the selected passages, and the citations point to the documents that survived selection. That means there are two chained contests: getting into the candidate set, and winning the re-rank.
What makes a page win retrieval
Being indexed and crawler-accessible is the prerequisite: a JavaScript-dependent page or a PDF with no text layer rarely reaches the candidate set. Next comes whatever makes extraction easy: a block that answers the sub-question on its own, with figures, dates and named entities sitting next to the claim they support.
Finally, the trust signals: named, verifiable authorship, a visible update date, coherence between what the page says and what other sources say about the same entity, and external signal pointing at the domain. Between two equally readable blocks, that is the tiebreaker.
Related terms
Retrieval operates on top of query fan-out and is fed by AI crawlers. See it in detail in how ChatGPT chooses the sources it cites.
Frequently asked questions
Does every AI answer go through retrieval?
No. Answers the model produces purely from what it learned in training retrieve nothing and usually carry no citations. When there are links in the answer, retrieval happened.
Which index do AI assistants retrieve from?
It varies by product and changes often: some use their own index, some license a search engine’s, and several combine both. That is why ReBo measures engine by engine rather than assuming a common index.
Can you force a page to be retrieved?
No. You can remove the obstacles (access allowed in robots.txt and at the CDN, static HTML, extractable structure) and raise the trust signals. What the system does with that is not controllable, which is why we do not promise citations.