Google's artificial intelligence assistant Gemini has just reached one billion monthly users, CEO Sundar Pichai said Tuesday, only a week after a major leadership shake-up in the tech giant's AI division.

"It's our fastest-growing product ever," and the 14th product to reach a billion users, Pichai posted on social media.

The milestone, which Google calculated based on how many people use the Gemini app across its ecosystem, gives the search giant a victory amid a major overhaul of its AI division.

Demis Hassabis, who won a Nobel Prize in chemistry, recently stepped back from the day-to-day management of Google DeepMind, the lab that designs the Gemini models. And several leading researchers left as well, including Jeff Dean, a central figure in the group's engineering efforts for nearly three decades.

Its new flagship model, Gemini 3.5 Pro, initially promised for June, still has not been released, while its rivals have launched several models which are considered more powerful, particularly for generating computer code, currently the most lucrative area in the sector.

In the face of this technological lag, Google's audience remains its main asset as it integrates AI into its ecosystem, from search and Gmail to Google Maps and YouTube.

OpenAI reached 1 billion users across all its interfaces, led by ChatGPT, the lab announced in July without specifying whether that figure was monthly or weekly users.

The San Francisco-based AI lab sparked the artificial intelligence boom when it launched its free ChatGPT app in November 2022, and thus built its user base from scratch in under four years.

Every audience metric feeds into the valuation that OpenAI hopes to achieve with an eventual public listing, for which it filed a confidential application in June.

In a sign of tightening competition against Gemini, China's DeepSeek, and its San Francisco rival Anthropic, which makes Claude, ChatGPT's market share for AI assistants fell below 50% in the first half of the year, according to research firm Sensor Tower, which uses company data to estimate usage.