Google Rebuilds Search Around Gemini 3.5 Flash — AI Mode Is Now the Default for Everyone
Gemini 3.5 Flash now powers AI Mode globally, in what Google calls the biggest change to Search in 25 years. AI Overviews reach 2.5 billion monthly users, and Google just published its first official GEO playbook.
Google has finished rolling out Gemini 3.5 Flash as the default model behind AI Mode for every user globally — a shift the company itself calls “the biggest change to Search in over 25 years.” The numbers back the claim: AI Overviews now reach 2.5 billion monthly users, and AI Mode crossed 1 billion users in its first year.
This is no longer an experiment bolted onto the classic results page. AI Mode builds responses on the fly — custom generative layouts, visual tools, simulations — shaped to the question instead of returning a ranked list of pages. Users can now attach images, documents, videos, and even open browser tabs directly to a query. Search is becoming a workspace, not an index.
For developers and site owners, the practical changes matter more than the headline. On June 3, Google shipped Generative AI Performance Reports in Search Console, giving native tracking of AI Overviews and AI Mode impressions by page, country, and device. For the first time, you can measure how often the AI layer surfaces your content — without third-party scraping tools. A content opt-out toggle followed on June 17, letting publishers remove pages from AI features without touching their organic rankings.
Google also published its first consolidated GEO (generative engine optimization) guide, and it reads like an admission that the rules have changed. Five content types reliably earn AI citations: original research, expert analysis, first-hand experience, unique data, and proprietary perspective. Thin aggregation earns nothing. And Google was blunt about one cottage industry: llms.txt files receive no special treatment. Stop shipping them expecting a ranking boost.
The advertising side is moving more cautiously. Google is testing AI-generated summaries beneath sponsored ads, but delayed the automatic upgrade of Dynamic Search Ads to AI Max from September 2026 to February 2027 — a sign that monetizing generative results is harder than generating them.
The takeaway is uncomfortable but clear. The ten blue links funded the open web for two decades, and the layer replacing them cites far fewer sources per query. If your traffic strategy is still “rank for keywords,” you’re optimizing for a shrinking surface. The sites that survive this transition will be the ones producing the five content types Google just told everyone it rewards.
Measure your AI impressions in Search Console this week. That baseline will matter in six months.