ChatGPT has 1.1 billion monthly users - more than the app has ever had. But its share of the AI assistant market just slipped below 50% for the first time.
The story isn't that ChatGPT is shrinking. It's that the rest of the field is catching up - and Claude is leading on paid conversion, the metric that drives revenue.
Gemini and Claude Take a Bigger Slice
ChatGPT controlled more than half the AI assistant market through January, according to Sensor Tower's State of AI Report for 2026. By the end of May, that share had fallen to 46.4%.
Gemini grabbed 27.7% and Claude pulled 10.3%, while everyone else - Grok, Perplexity, DeepSeek, Meta AI - sits under 5%.
Gemini's climb owes a lot to Google plugging it into Search, Workspace, and Android by default, which means tens of millions of users get exposed to it without ever downloading an app.
Claude built its share the harder way - by earning a reputation for getting actual work done on coding and writing tasks, where developers and analysts have flocked to it.
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The Number Investors Should Actually Watch
Market share grabs the headlines, but paid conversion - the rate at which free users become paying ones - pays the bills.
13% of Claude's users now pay for a subscription - the highest rate in the category, and the kind of number that turns user growth into actual revenue.
That matters because most AI assistants are still free, which means revenue depends on turning heavy users into paying ones. Claude's $20-a-month Pro tier is doing exactly that, helped by power users in coding, research, and writing workflows where free limits hit fast.
The broader spending picture backs the trend. Users are on pace to spend $4.2 billion on AI apps in the first half of this year, more than double the $1.83 billion they spent in the same period a year ago.
The industry is no longer racing to add users - it's racing to charge them.
What To Watch
OpenAI's answer is ads. By May, 17% of daily ChatGPT users were seeing them, up from near-zero when OpenAI began experimenting with ads in February, with software and shopping brands buying the most slots.
That shopping piece matters. ChatGPT is now sending more referral traffic to Walmart, Target, and Costco, while Amazon - which blocked ChatGPT's crawlers last November - is getting left out.
Walmart's own shopping AI is also gaining ground on Amazon's Rufus, which has seen flat user growth.
The next read comes when the major platforms report earnings - Microsoft, Google, Amazon, and Meta are all expected to break out fresh user and revenue numbers for their AI assistants. [NEEDS MANUAL VERIFICATION - forward-looking editorial claim not in source]
The AI app race used to be about who had the most users. Now it's about who can charge them, and Claude's conversion numbers are the early scorecard.
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