Dynamic AI Overview expansion does not rewrite the impression rule

On 28 August 2026 Google confirmed that, for some queries, AI Overviews may dynamically expand to a full response: the compact "Show more" state can open automatically, the expanded Overview sits above classic results, and expansion is cancelled if the user has already started scrolling. That is a SERP presentation change. It is not, on the published Help Center pages, a rewrite of how Search Console counts impressions for links inside AI Overviews.

Question. Under Google's published impression methodology, what becomes countable when an AI Overview expands dynamically, and what remains undocumented after the 28 August 2026 confirmation?

Method. Documentation-plane audit on 7 September 2026 of: Search Console Help answer 7042828 (impressions / position / clicks, including the AI Overviews and AI Mode sections); Help answer 16984139 (Generative AI performance report, Search); the AI features site-owner guide; Search Engine Land and The Verge reports of Google's 28 August 2026 confirmation (spokesperson statements). No property CSV export. No SERP scrape treated as a primary fact. Third-party CTR studies are cited only as industry context, not as Google documentation.

Result: what Google documented before the expansion news

Fact. Help answer 7042828 defines an impression as a user having seen (or potentially seen) a link to your site. The general rule: an impression is counted when an item appears in the current page of results even if it is not scrolled into the viewport, as long as the user does not need to click to see more results. Inside independently scrolling or expanding widgets (carousels, FAQ-style expanders), the item must typically be scrolled into view within the widget, or expanded by a click, before an impression registers. (Help Center.)

Fact. For AI Overviews, the same page states: a click to an external page counts as a click; standard impression rules apply; and, in the English Help Center wording retrieved for this note, to be counted as an impression, the link must be scrolled or expanded into view. An AI Overview occupies a single position; every link inside it is assigned that same position. Search Labs experiments are excluded. (Help Center, AI Overviews section.)

Fact. For AI Mode, standard impression rules apply; position follows ordinary Search-results methodology; a follow-up question is a new query for counting purposes. (Help Center, AI Mode section.)

Fact. The Generative AI performance report (Search) counts impressions in AI Overviews and AI Mode, with dimensions for pages, countries, devices, and dates. It does not list Queries, Clicks, CTR, or Position as fields of that dedicated report. Impressions there are "how many times links to your site were shown to a user in a generative AI feature." (Help Center 16984139; prior Casinokrisa note on the report as an impression ledger.)

Result: what the 28 August 2026 confirmation actually said

Fact. Search Engine Land (28 August 2026) reported Google's confirmation that for some queries AI Overviews may dynamically expand to a full detailed response, removing the need to click "Show more," and pushing core results further down. If the user has already begun scrolling to content below the Overview, Google cancels the expansion so the user does not lose reading position. Google's quoted framing: expansion happens "for topics where our systems determine it's most useful for people," and Google's research claims users find Search more helpful and engage deeper in follow-up exploration. (SEL.)

Fact. The Verge (28 August 2026) attributed the same expansion and scroll-cancel behavior to Google spokesperson Jennifer Kutz, with the same "most useful" and deeper follow-up framing. The Verge notes the behavior is not consistent across queries and sessions. (The Verge.)

Fact. Neither the SEL nor Verge pieces, as retrieved for this audit, publish a new Search Console dimension, a revised Help Center impression definition, or a documented percentage of queries affected. The product change described is SERP chrome and answer length, not a new analytics schema.

Interpretation

In indexing-first terms, eligibility for AI Overview supporting links still starts at crawl -> index -> snippet eligibility (AI features guide). The Generative AI report still records shown links, not "we authored the sentence." Dynamic expansion changes how much of the Overview is visible without a click, and how far classic results sit below the fold.

Under the published impression rules, two mechanical readings matter:

1. Links that were gated behind "Show more." If those links previously required an expand click before they counted, automatic expansion can move them into the "expanded into view" state without that click -- when the Overview actually expands and the link becomes visible under the documented scroll/expand rule. That is a presentation-triggered change in when the existing rule can fire, not a new metric called "dynamic expansion impressions."

2. Links that were already in the compact viewport. Those were already in the current results surface. Expansion mainly changes how much additional Overview content and how many additional supporting links become available without user action, and how much scrolling classic results require.

What you still cannot conclude from Console alone: which queries expanded, whether your URL was the grounding source of a sentence, or what CTR "should" be after expansion. Position for every link inside an Overview remains the Overview's single position on the classic counting page -- so "we dropped from position 3 to 11 because of expansion" is a misuse of that shared-position rule unless you are talking about classic blue links below the Overview, which are a different element.

Treat press CTR estimates as industry measurement, not as Google documentation. This note does not validate third-party click-loss percentages against any property export.

Limits

• Documentation-plane only; no casinokrisa.com or client CSV.
• Help Center heuristics are explicitly subject to change.
• Dynamic expansion is query-conditional and can cancel on early scroll; a lab SERP is not a stable sample.
• Absence of an expand-state dimension in the Generative AI report is a documentation fact for this date, not a permanence claim.
• Spokesperson quotes are taken from SEL / Verge reporting of Google's confirmation, not from a Search Central Blog post.

Takeaway

Date the SERP chrome separately from the ledger. On 28 August 2026 Google confirmed dynamic AI Overview expansion for some queries. On 7 September 2026 the published Search Console methodology still says AI Overview link impressions follow standard rules and require the link to be scrolled or expanded into view. Expansion can change when that rule fires for links that used to sit behind "Show more." It does not, on these pages, invent a query index, a citation label, or an expand-state column. Keep reading the Generative AI performance report as an impression ledger -- and keep classic Performance for Web traffic that includes AI-feature clicks under the ordinary bagging rules.

Suggested citation

Mikhail Drozdov. "Dynamic AI Overview expansion does not rewrite the impression rule." Casinokrisa Research, 7 September 2026. https://casinokrisa.com/blog/aio-dynamic-expand-impression-rules-2026-08

Mikhail Drozdov is an AI Search & Indexing Systems Researcher. Casinokrisa is the research platform. Person URL: https://casinokrisa.com/person/mikhail-drozdov