ChatGPT's rapid expansion is showing signs of cooling, while Google's Gemini picks up speed, new research by Sensor Tower shows.
ChatGPT still holds the top spot in the AI assistant space. Data from Sensor Tower shows that OpenAI captures half of all worldwide mobile downloads and accounts for 55% of people using AI chatbots each month around the globe. However, Google's competing product is now growing faster across three key areas: new downloads, monthly active users, and average user engagement time.
The numbers have caught OpenAI's attention. A recent "code red" memo from CEO Sam Altman instructed workers to focus on improving the company's AI tools. The note highlighted several areas needing improvement, including making responses more personal, enhancing the system's functionality, and creating more effective images.
Growth Numbers Tell Two Different Stories
The competition isn't finished yet. Both products continue adding users at a strong pace. ChatGPT saw its worldwide monthly user base jump 180% compared to a year earlier, reaching a record 11.5 million users in November 2025. Gemini wasn't far behind with 170% growth over the same period.
But a closer look at recent months tells a different story. From August to November, ChatGPT's monthly users worldwide increased by just 6%, reaching approximately 810 million people. Sensor Tower suggests that this small increase might indicate the product is approaching a ceiling in terms of the number of people who want to use it.
Google's Gemini moved much faster during those same months, with monthly users climbing about 30%. The jump came after the company released Nano Banana, its new tool for creating images, which attracted more users.
Google's Android Advantage Could Change the Game
Google has another edge that could matter more as time goes on. About twice as many Android phone users in the United States now work with Gemini straight through their phone's operating system instead of opening a separate app. Since Android dominates the phone market worldwide, this built-in access gives Google a way to reach people beyond just those who download an app or visit a website.
Looking at the bigger picture of AI chatbots, which includes ChatGPT, Copilot, Claude, Perplexity, and Grok, Gemini is grabbing a bigger slice. Between May and November 2025, Gemini picked up three percentage points more of all monthly users across these apps.
ChatGPT went the other direction. From August through November 2025, it lost three percentage points of its share of monthly users.
Other challengers are also making waves. Both Perplexity and Claude saw their user numbers more than double in 2025. Perplexity shot up 370% compared to the previous year, while Claude grew 190%.
The download numbers paint a similar picture. ChatGPT's worldwide downloads rose 85% compared to a year ago as of November. But that fell short of the 110% average growth seen across all major AI chatbots.
Perplexity and Gemini led the pack in download growth, jumping 215% and 190% respectively when compared to the year before.
How long people spend using these apps also shows the shift happening. Gemini users more than doubled their time in the app over several months, according to Sensor Tower. By November, people spent an average of 11 minutes per day using Gemini, a 120% increase since March. The company credits Nano Banana's success after its September launch.
ChatGPT users only increased their daily time by 6% during the same stretch. Even more concerning for OpenAI, time spent using ChatGPT dropped 10% when comparing November to July.
While Google appears to be catching up to the market leader, much of its recent success ties back to Nano Banana. OpenAI could regain momentum if it releases new products that make a similar impact on users.