ChatGPT's market share dropped below 50% for the first time, falling to 46.4% by the end of May as users migrate between AI assistants at rates that signal the end of OpenAI's dominance over the category.
Sensor Tower's State of AI Report for 2026 shows ChatGPT still leads with over 1.1 billion monthly users, followed by Google's Gemini at 662 million and Anthropic's Claude at 245 million. But the trajectory has shifted.
ChatGPT commanded more than half the market as recently as January. By the end of May, Gemini had climbed to 27.7% and Claude to 10.3%, according to the analytics firm.
The chatbot that became the fastest app ever to reach 1 billion monthly users now faces a market where switching behavior is accelerating. OpenAI's $200 million contract with the U.S. Department of Defense in February triggered a measurable spike in ChatGPT uninstalls, a sign that brand trust and values alignment matter to users as much as capability.
Gemini's gains are powered by integration with Google's broader ecosystem of tools. Claude has built a reputation for productivity use cases and is closing in on ChatGPT's user retention rate.
The revenue picture is shifting faster than the user numbers. AI assistant spending is on pace to hit $4.2 billion in H1 2026, nearly double the $1.83 billion in H1 2025.
Claude leads all platforms in subscription conversion with 13% of its 245 million users paying, suggesting that revenue efficiency is becoming as important as raw user counts.
Total hours spent on AI apps are projected to rise from 17.2 billion in H1 2025 to roughly 36 billion in H1 2026. The top three assistants command 89% of that time. Download and spend growth rates have decelerated, indicating market maturation even as absolute numbers climb.
Asia recorded its first download decline of 3.3% in Q1 2026, driven by dips in China and India. Despite leading in total downloads, the region trails North America and Europe in in-app spending. OpenAI began experimenting with ads in ChatGPT in February. By May, an average of 17% of daily users were being served ads.
Software and shopping are the largest advertiser categories so far, followed by media and entertainment and food and dining. The company is also deepening shopping integrations, sending referral traffic to retailers like Target, Walmart, and Costco. Amazon, which blocked ChatGPT's web crawlers, has seen stagnant referral traffic from the platform.
