What AI model does it use?

What AI model does Google Search use?

Google's search AI is really two features. AI Overviews are the summaries that sometimes appear above the ordinary results; AI Mode is the separate chat-style search you switch into. They don't share a model, and Google's documentation for site owners says so outright: "AI Mode and AI Overviews may use different models and techniques."

AI Mode runs Gemini 3.5 Flash by default

At Google I/O on May 19, 2026, Elizabeth Reid, who runs Search, wrote that Google was "upgrading Search with Gemini 3.5 Flash... as the new default model in AI Mode for everyone globally." Flash is Google's faster, cheaper tier of Gemini (Pro is the bigger one). Four months on, that's still the newest default I could find for free users.

Paying subscribers have a newer model (AI Pro and Ultra are Google's paid AI plans). Google's September 2 post on Gemini 3.8 Flash says it "is available to Google AI Pro and Ultra subscribers across the Gemini app, AI Mode in Google Search and Gemini in Google Sheets." None of the posts I read extend 3.8 Flash to everyone else.

There's a small picker inside AI Mode too. The AI Mode help page says you can use Gemini 3 Pro "by selecting "Pro" from the menu" in the search bar, with daily limits. It still says Gemini 3 Pro, which is a generation behind the Flash default (I'm not sure whether the page is stale or the Pro option really is older, and Google's posts don't settle it).

Gemini 3 runs AI Overviews

The summaries above the results changed model on January 27, 2026, when Robby Stein, a vice president of product for Search, wrote that "Gemini 3 is now the default model for AI Overviews". I found nothing newer. That surprised me, given how often AI Mode's model has moved. "Gemini 3" on its own could be a Flash or a Pro variant, too, so even the name is loose.

Harder questions can get a bigger model

In November 2025, launching Gemini 3 in Search, Google said it would "intelligently route your most challenging questions in AI Mode and AI Overviews to this frontier model", while "continuing to use faster models for simpler tasks." That routing went first to Google AI Pro and Ultra subscribers in the US.

So the model behind a search depends on how hard Google judges the question, which plan you pay for, and which of the two features answers. Two searches a minute apart can get different Gemini models. The results page won't tell you which one you got.

How the defaults moved

Gemini 3 Flash became the AI Mode default in December 2025. A month later Gemini 3 took over AI Overviews, then 3.5 Flash replaced 3 Flash in AI Mode in May, and 3.8 Flash reached paying subscribers in September. Every one of those was Google's own model; I'd half expected a partner model somewhere in the fine print, and there wasn't one.

What's left unsaid

Which model answers a particular search is decided per query, and you can't see it. Which Gemini 3 variant runs AI Overviews is unstated too. For free users in AI Mode, the last model Google named is Gemini 3.5 Flash.