ChatGPT is no longer the AI app most people use. It's just the one most people have.
For the first time since Sensor Tower started tracking the category, ChatGPT's share of unique AI users across mobile and web slipped below 50% in March, according to the firm's 2026 State of Mobile report. Gemini and Claude picked up the rest.
Then in May, ChatGPT crossed one billion monthly active users on mobile, becoming the fastest app ever to do it, beating TikTok, Instagram and YouTube to that milestone. So the king of the category lost its majority and hit a billion users in the same quarter. Both things are true.
What's actually happening is that the pie is exploding. Sensor Tower projects global time spent inside generative AI apps will more than double year over year, from 17.2 billion hours in the first half of 2025 to 36 billion in the first half of 2026. Inside that bigger pie, three apps (ChatGPT, DeepSeek and Gemini) now account for nearly 90% of total time spent. The market isn't fragmenting into chaos, it's settling into a tight oligopoly that just happens to no longer be a monopoly.
Claude is the one quietly making the most money on the way up. Its US mobile revenue per user climbed from under $0.50 last September to $2.76 in May, according to Forbes citing Sensor Tower data. That's more than five times what ChatGPT pulls in on the same metric, even though Claude is a fraction of its size. The story people have been telling about Anthropic, that it's smaller but the enterprise economics are better, is now showing up on the consumer side too.
Gemini's wedge looks different. Google doesn't have to win users one at a time when it can just be the default. Apple confirmed in January that the next Siri will run on Gemini, with the company saying Google's tech "provides the most capable foundation" for what Apple wants to build. That one deal puts Gemini in front of hundreds of millions of iPhone users who will never open the Gemini app.
The bear case here writes itself. Public sentiment around AI is getting worse, ChatGPT lost the majority, and the smaller players are scaling fast. But the user behavior tells a different story. Tom Grant, VP of research at Apptopia, told eMarketer that the real signal isn't the download numbers, it's that churn is dropping sharply across the category, meaning people are actually sticking around once they show up. Y Combinator CEO Garry Tan put it more bluntly when he looked at the retention curves and asked, "Does a hype cycle have a retention curve that looks like this?"
INTO THE VALLEY
The interesting thing about ChatGPT losing the majority isn't that it lost. It's what it lost to. A year ago the worry was that OpenAI would just run away with the category the way Google ran away with search. Instead what's forming looks more like a three-way split where ChatGPT owns scale, Gemini owns distribution through the devices people already use, and Claude owns the wallet. Each one is a different bet on what actually matters in this market, and right now all three are working. The next thing to watch isn't who hits a billion users next. It's whether Claude's per-user economics hold up as it grows, because if they do, the most valuable AI company won't be the one with the most people in the app.
