Four years after OpenAI launched ChatGPT at the end of 2022, the service has crossed the one-billion monthly active user threshold even as its share of the AI chatbot market has declined.
According to the latest Sensor Tower report, by May 2026 ChatGPT's market share had dropped to 46.4 percent. It is followed by Google Gemini with 27.7 percent and Anthropic Claude with 10.3 percent.
- Monthly active users (Sensor Tower, May 2026):
- ChatGPT: 1.1 billion
- Google Gemini: 662 million
- Anthropic Claude: 245 million
While a 46.4 percent share remains a strong position, the decline is notable given OpenAI's early-mover advantage in generative AI chatbots. The drop illustrates how competition has intensified since ChatGPT's debut.
The report draws a comparison to Google Chrome: the browser held a dominant market share above 90 percent for years and only fell below 90 percent in early 2025, despite the emergence of multiple rivals. The analogy highlights that being first to market does not guarantee perpetual dominance in a rapidly evolving sector.
Sensor Tower also notes that ChatGPT's shrinking market share coincides with growth in its user base: the service had 1.1 billion monthly active users at the beginning of May 2026, making it not only the first chatbot to reach that milestone but also one of the fastest-growing online applications.
Spending on these applications has increased as well. Expenditures on chatbot services rose to $4.2 billion in the first half of this year, up from $1.83 billion in the first half of the previous year.
Although ChatGPT leads in total monthly users, Anthropic Claude reportedly has the largest number of paying users. Sensor Tower attributes this primarily to Anthropic substantially reducing the capabilities of Claude's free tier, which likely pushed more users toward paid subscriptions.
Overall, the latest figures depict a market with rapidly expanding user numbers, growing revenues from paid models, and increasing competition that is eroding the market share of early leaders.
