ChatGPT’s grip on the AI assistant market has loosened for the first time, with its global share slipping below 50 percent as rivals rapidly gain ground. New data from analytics firm Sensor Tower shows that while OpenAI’s chatbot remains the most widely used assistant, users are increasingly willing to experiment with alternatives such as Google’s Gemini, Anthropic’s Claude, and xAI’s Grok.

ChatGPT still leads the field with more than 1.1 billion monthly users, after becoming the fastest app in history to reach 1 billion monthly active users. Gemini follows with 662 million monthly users, and Claude with 245 million, underscoring how quickly the market has diversified since the first wave of generative AI enthusiasm.

Until recently, ChatGPT commanded more than half of all AI assistant usage worldwide. By the end of May, however, its share had fallen to 46.4 percent, according to Sensor Tower’s State of AI Report. Gemini now accounts for 27.7 percent of the market and Claude 10.3 percent, while smaller players including Grok, Perplexity, DeepSeek, and Meta AI each hold under 5 percent.

The report suggests that users are not locked into a single assistant. Feature launches, policy changes, and corporate partnerships are prompting people to switch. OpenAI’s deal with the U.S. Department of Defense, for example, coincided with a noticeable spike in ChatGPT uninstalls, indicating that trust and perceived values are becoming competitive differentiators alongside raw capability.

At the same time, the broader AI app economy is shifting from explosive growth to monetization. Sensor Tower estimates that people will download nearly 2.3 billion AI apps in the first half of the year and spend more than 4.2 billion dollars on them, up sharply from the previous year but with slower growth rates. Time spent in AI apps is projected to more than double to roughly 36 billion hours, with the top three assistants capturing 89 percent of that engagement.

Regional patterns are also diverging. Asia, despite leading in total downloads, has seen a small decline in new installs and lags North America and Europe in in-app spending. In the United States, users are leaning heavily on assistants for productivity, and Claude stands out with an estimated 13 percent of its users paying for subscriptions, the highest conversion rate among major players.

OpenAI has begun layering advertising onto ChatGPT, gradually increasing the share of users who see ads and the volume of placements. Software and shopping brands dominate early campaigns, as ChatGPT’s recommendations start to influence where and how people spend money online.