Google's Gemini app crossed 900 million monthly active users in May 2026, a milestone that puts it level with the weekly active user count reported for ChatGPT in February and marks a sharp acceleration in the competitive race between the two largest AI assistant platforms.

The figure comes from Alphabet's quarterly earnings calls and press releases, as compiled by EMARKETER Chief Content Officer Vladimir Hanzlik in a LinkedIn post published today. The data point is significant not only for its absolute size but for what it reveals about relative growth rates. According to Hanzlik, Gemini added 20% monthly active users in the four months to May 2026, compared with ChatGPT adding just 12.5% weekly active users in the four months to February 2026.

The 900 million figure in context

Reaching 900 million monthly active users does not automatically mean Gemini has caught ChatGPT. The comparison is complicated by the fact that the two platforms report different engagement metrics. ChatGPT discloses weekly active users; Gemini discloses monthly active users. Those are not directly equivalent measures.

According to Hanzlik, if one assumes ChatGPT has 1.5 times as many monthly active users as weekly active users - a proxy he described as reasonable in a prior post - then ChatGPT would stand at approximately 1,350 million monthly active users against Gemini's 900 million. That would represent a gap of 450 million monthly active users in favour of ChatGPT.

The caveat matters. A platform reporting monthly figures will naturally look larger than one reporting weekly figures, because a user who opens an app three times in a month counts once for a monthly metric and potentially three times for a weekly metric across the same period. Comparing the two requires assumptions, and assumptions introduce uncertainty.

What is not in dispute is the trajectory. Gemini's growth rate in the four months to May 2026 - 20% - exceeded ChatGPT's equivalent growth rate of 12.5% in the four months to February 2026. According to Hanzlik, even if ChatGPT reaches one billion weekly active users in June 2026, it would have added 100 million weekly active users - or approximately 150 million monthly active users using the proxy - over four months. That would match, but not exceed, the 150 million monthly active users Gemini added over the same period.

The implication, according to Hanzlik, is that "Gemini might well be on track to displace ChatGPT as the number one consumer LLM."

A growth trajectory built on product integration

Gemini's rise from a standing start to 900 million monthly active users in roughly two years reflects Google's ability to distribute AI capabilities across an installed base that no standalone AI company can replicate.

In August 2025, Gemini reached 450 million monthly active users. By October 2025, that figure had climbed to 650 million, a gain of 200 million in a single quarter, driven partly by the release of the Nano Banana image generation tool and the deepening integration of Gemini into Android devices. Alphabet reported the 750 million figure on February 4, 2026, as part of its fourth quarter 2025 earnings announcement. The 900 million figure now disclosed for May 2026 continues that upward curve.

The growth did not happen purely through word of mouth. PPC Land reported in December 2025 that Google had been automatically routing Google Assistant queries to Gemini on devices where users had both services installed - a distribution mechanism that inflates raw active user counts in ways that organic adoption alone would not. That context is relevant when evaluating the headline numbers.

Despite that caveat, the scale is real. Gemini's traffic share in the broader AI assistant market reached 22% as of January 2026, up from 5.3% twelve months earlier - a 315% increase in twelve months, as PPC Land tracked through Similarweb data published January 22, 2026. In Q1 2026, Gemini continued expanding its share of AI tool visits, climbing from 10.41% in November 2025 to 16.06% in the US by March 2026.

ChatGPT's position and OpenAI's own milestones

ChatGPT's user figures have also grown substantially. OpenAI reported 700 million weekly active users in August 2025. On February 27, 2026, OpenAI disclosed that ChatGPT had reached 900 million weekly active users, simultaneously announcing a $110 billion funding round and a strategic partnership with Amazon involving a $50 billion investment. The jump from 700 million to 900 million weekly active users in roughly six months represented significant absolute growth, even if the pace lagged Gemini's percentage gains over a comparable window.

The 900 million weekly active user figure for ChatGPT, reported in February, is the number that Gemini's 900 million monthly figure now matches in raw terms. But the methodological difference - weekly versus monthly - makes that a partial comparison at best. A user counted weekly who opens the platform twice a week registers differently from a user counted monthly who opens it twice in thirty days.

ChatGPT had 700 million weekly active users when OpenAI first confirmed its advertising plans on January 16, 2026, according to PPC Land's coverage of that announcement. The advertising pilot formally launched on February 9, 2026, with a minimum spend threshold of $200,000 to $250,000, limited initially to holding company and agency partners. The ChatGPT Ads Manager subsequently opened to all US businesses with CPC bidding, and conversion optimization tools followed, making ChatGPT a more direct competitor to established paid media channels.

Gemini beyond the app: AI Overviews and AI Mode

Hanzlik's analysis includes a point that reframes the competitive picture further. According to his post, Google's AI Overviews and AI Mode "both have more monthly users than Gemini." AI Overviews, the AI-generated summaries appearing at the top of Google Search results, now serve more than two billion monthly users. AI Mode, the conversational search experience, surpassed one billion monthly active users globally as of May 19, 2026, the same month Gemini hit 900 million.

Those figures mean that Google's aggregate exposure to AI-mediated consumer interactions - across the Gemini app, AI Overviews, and AI Mode - runs to billions of users per month, well above any figure OpenAI has reported. The Gemini app is, by that reading, only one surface in a much larger AI ecosystem that Google has embedded into its core search and productivity products.

That integration was underscored at Google I/O on May 19, 2026, when the company announced a sweeping set of changes to Search, including the deployment of Gemini 3.5 Flash in AI Mode, the introduction of persistent background agents, and the rollout of Personal Intelligence - a feature that allows AI Mode and the Gemini app to draw on data from a user's own Gmail, Google Photos, and eventually Google Calendar when composing responses.

The concentration of AI interaction on Google surfaces raises questions for advertisers and publishers alike. Alphabet's Q1 2026 earnings, reported on April 30, showed Google Network advertising revenue falling 4% year-on-year to $6.97 billion - the steepest decline in the series - as AI-generated answers on Google's own pages reduced the incentive for users to click through to external websites. That trend has direct consequences for the publisher ecosystem that programmatic advertising depends on.

What the user numbers mean for marketers

The competition between Gemini and ChatGPT is not purely a product race. It has structural implications for where consumers spend attention, and therefore for where advertising budgets will eventually flow.

Edison Research data published in May 2026 found that 65% of American adults - approximately 175.5 million people - used at least one AI platform in the week of May 14-18, 2026, up from 52% in February 2026, an increase of more than 35.6 million weekly users in three months. Gemini recorded the fastest growth of any platform measured, rising from 25% weekly reach to 38% among US adults. ChatGPT led with 43% weekly reach.

Those figures describe a different competitive dynamic from the global monthly active user counts. In the US adult population measured weekly, ChatGPT still leads but Gemini is closing ground at a faster pace. The gap between 43% and 38% is narrow and narrowing.

For marketers, the stakes extend beyond reach. ChatGPT has moved to monetise its user base through advertising, with conversion optimisation tools now available through the ChatGPT Ads Manager. Google, by contrast, has maintained that Gemini itself will not carry advertising in the near term, with a vice president explaining the strategic separation between the chatbot and Google's ad-supported search surfaces in January 2026. The monetisation paths are therefore different: OpenAI is building a direct ad platform, while Google is concentrating commercial activity inside AI Overviews and AI Mode within Search.

Whether that distinction holds as Gemini approaches and potentially exceeds ChatGPT's active user base remains an open question. At 900 million monthly active users, and with a growth rate that currently exceeds ChatGPT's equivalent metric, Gemini has moved from a distant second to a credible challenger. The underlying numbers - complicated by different measurement conventions - do not yet show Gemini in front. But the trajectory does show it catching up.

Timeline

Summary

Who: Google's Gemini app and OpenAI's ChatGPT are the two platforms at the centre of this analysis. The data is drawn from Alphabet's quarterly earnings calls and press releases, and from OpenAI's public disclosures, as compiled by Vladimir Hanzlik, Chief Content Officer at EMARKETER.

What: Gemini reached 900 million monthly active users in May 2026. That figure matches the number of weekly active users ChatGPT reported in February 2026. Gemini added 20% monthly active users in the four months to May 2026, a faster pace than the 12.5% weekly active user growth ChatGPT posted in the four months to February 2026. The comparison is complicated by the different measurement intervals each platform uses.

When: The Gemini figure is for May 2026, disclosed today through Alphabet's earnings reporting and compiled by EMARKETER. The ChatGPT comparison figures span August 2024 through February 2026, with the most recent ChatGPT weekly active user count of 900 million disclosed on February 27, 2026.

Where: Both platforms operate globally. The user figures are worldwide counts, not regional ones. Separate US-specific data from Edison Research and Datos reflects different dynamics at the national level.

Why: The figures matter for the marketing industry because they define the scale of the two largest AI assistant platforms at a moment when both are becoming advertising surfaces - ChatGPT through a formal Ads Manager, and Google through AI Overviews and AI Mode within Search. Gemini's faster growth rate, combined with Google's broader ecosystem of two billion AI Overview users and one billion AI Mode users, positions Google as the dominant aggregator of AI-mediated consumer attention. How that attention is monetised - and whether Gemini itself eventually carries advertising - will shape the structure of digital advertising over the next several years.