Context
Sünkler and colleagues published an ACM WebSci Companion audit of 900 English health queries on Google US, collected February 2–4, 2026. AI Overviews appeared for 87.7% of this constructed query set, and the average observed domain-level overlap between AI-cited sources and the organic top ten was 46.2%. YouTube represented 6.8% of AI citations versus 0.6% of organic results in the sample.
What changed
The peer-reviewed observational audit compares AI Overview activation, top-ten organic source overlap, and domain distribution in a controlled US health-query snapshot using a browser-extension data collection method.
Why it matters
AI citation visibility and organic search ranking are distinct measurements. Site owners and researchers need to measure AI Overview activation, citation share, source overlap and platform differences rather than infer them from classic SERP ranks.
Visibility OS interpretation
Visibility OS interpretation: the study supports stage-specific AI source-selection auditing. It does not show that Google universally favors user-generated media, that YouTube health content is inaccurate, or that these patterns persist beyond the observed February 2026 snapshot.
What remains uncertain
Would the observed overlap and domain composition replicate across topics, languages, locations and later model versions? How would a medical expert rate the cited video evidence? What fraction of observed citations leads to site visits?