At Google I/O on 19 May 2026, Google announced that Gemini 3.5 Flash is now the default model behind AI Mode in Google Search, rolling out worldwide in every language AI Mode supports. The company said AI Mode has surpassed one billion monthly users in the year since launch, with queries doubling every quarter. Two days later, on 21 May, Google began rolling out the May 2026 core update — its fourth ranking change this year and the second core update.
What Google announced at I/O
Google described a redesigned Search box as the "biggest upgrade in over 25 years," with dynamic expansion, AI-powered suggestions and multimodal inputs covering text, images, files, videos and Chrome tabs. Follow-up questions in AI Overviews are live on desktop and mobile worldwide.
A new class of information agents will launch "this summer" for Google AI Pro and Ultra subscribers. The agents monitor blogs, news sites, social posts and real-time data on the user's behalf, with booking and service agents expanding to local categories in the United States over the same window. Personal intelligence features have expanded to roughly 200 countries and 98 languages with no subscription required.
What Google says SEO teams should do
Google's own guidance for AI features, last updated on 15 May 2026, frames AI Mode optimisation as ordinary search optimisation. Pages must be "indexed and eligible to be shown in Google Search with a snippet" to qualify. Beyond that, Google points to standard fundamentals: unique, helpful content with original viewpoints; clear headings and sections; semantic HTML; structured data where it already earns rich results.
Several things are explicitly ruled out. Google says structured data is "not required for generative AI search," there is no special schema for AI, no value in creating llms.txt files, no need to chunk content into smaller pieces and no reason to rewrite copy "for generative AI search." AI Mode selects sources using retrieval-augmented generation against the core Search index plus a "query fan-out" technique that issues several related queries in parallel.
In Google's framing, this means AI Mode and classical search are not separate optimisation disciplines — both draw from the same index, the same ranking signals and the same eligibility rules. A page that does not rank in Search is not a candidate for AI Mode citation either.
Where the practitioner debate is
The May core update arriving two days after I/O has been read by some SEO practitioners as connected to the model swap. Marie Haynes, founder of Marie Haynes Consulting, told Search Engine Journal the timing "makes sense seeing as Gemini 3.5 Flash is now powering the AI features of Search." Harpreet Singh Chatha, an SEO and AI search consultant, said the update may target sites doing "dumb [things] to show up in AI answers."
Search Engine Journal also reported user behaviour data Google shared at I/O: AI Mode queries are roughly three times longer than traditional searches, follow-up queries grew 40 per cent month-on-month in the United States, multimodal searches account for more than 16 per cent of usage, and "planning" queries are growing 80 per cent faster than AI Mode overall.
Jake Ward, founder of Mentions, framed the shift as "visibility greater than clicks." Alisa Scharf, chief AI officer at Seer, noted the measurement gap: "Can't optimise what you can't measure." Chris Long of Nectiv said practitioners should still track the llms.txt debate even though Google has dismissed it.
Google has not said when, or whether, AI Mode becomes the default Search experience for non-opted-in users. Information agents and agentic coding for AI Pro and Ultra subscribers are scheduled for the summer, with no specific date. The May 2026 core update is still rolling out and may take up to two weeks; Google has published no companion blog post or stated goals for it.
Sources
- Google blog — Google Search's I/O 2026 updates: AI agents and more
- Google blog — Gemini 3 Flash is rolling out globally in Google Search
- Google Search Central — Optimizing for Generative AI Features on Google Search
- Search Engine Journal — Google Launches Core Update Amid I/O AI Search Overhaul
- Search Engine Roundtable — Google May 2026 Core Update Landed Over The Weekend
