When Google reads your website, it does not decide whether the whole page is relevant to a search query. It reads paragraph by paragraph. If one specific paragraph answers a question clearly and directly, that paragraph can appear in an AI Overview even if the rest of the page is about something different. This is what Google calls passage indexing, and it changes exactly what optimising for search means.
The practical implication is that every paragraph on every page is a separate opportunity. A page that ranks for five keywords could, with proper passage structure, earn AI Overview citations for twenty different queries - one per well-written paragraph. The AEO content principles that govern how to write those paragraphs are all downstream of this single architectural fact.
Page document
Vector space
AI Overview result
Googlebot fetches the URL. The raw HTML is parsed and passed to the passage extraction pipeline. The page as a whole is not what gets indexed here - individual text segments are.
Passage Quality: Real Before and After
Three query examples showing exactly what separates a low-retrieval-score passage from a high-retrieval-score one. Select a query, then toggle between the bad and good version.
“Google has long been interested in making search more useful for its billions of users. One of the ways it does this is through various improvements to its core algorithm. In 2020, the company announced a significant change that affected how content is understood and ranked across the web.”
Context-before-answer: the query is not answered anywhere in this passage.
Vague: no specific information that a retrieval model can score against the query.
The answer is being withheld and deferred to content below - classic low-retrieval-score pattern.
Hover a zone to see explanation
Passage Quality Self-Scorer
Rate your passage against each criterion. The scoring model reflects the factors that Google's passage retrieval pipeline weighs most heavily.
Does the first sentence directly answer the target query?
Can the passage be understood without reading surrounding content?
Does the passage contain specific names, numbers, or named findings?
Is the passage 80 to 200 words?
Does the target query keyword appear in the passage?
This passage needs a fundamental rewrite. Start with the opening sentence - it must directly answer the query before any context or preamble.