ChatGPT's share of the AI assistant market fell to 46.4% by the end of May, according to Sensor Tower's 2026 State of AI report, ending its run above the 50% mark that had held since January. Google Gemini climbed to 27.7%, while Anthropic's Claude reached 10.3%, pointing to a market now led by three major players instead of one dominant app.
ChatGPT still leads by monthly active users
On absolute scale, ChatGPT remains the largest AI assistant globally with more than 1.1 billion monthly active users. Gemini follows with 662 million, and Claude stands at 245 million. The user gap is still wide. The faster story is the shift in share, with ChatGPT slipping from above 50% in January to 46.4% within four months.
Sensor Tower said other assistants including Grok, Perplexity, DeepSeek and Meta AI together account for less than 5% of the market. That keeps the sector highly concentrated even as competition intensifies among the largest platforms.
Users are switching between assistants more often
The report also points to a broader change in behavior: people are becoming more willing to use multiple AI assistants rather than staying with one. In some cases, outside events can accelerate that shift. After OpenAI signed a contract with the US Department of Defense in February, ChatGPT saw a 295% spike in uninstall volume, showing that trust and brand perception can affect user decisions as much as product features.
Gemini's momentum has been supported by tight integration with the Google ecosystem. Claude has built traction in productivity-focused use cases, and its retention is moving closer to ChatGPT's. In the US market, 13% of Anthropic users have converted to paid subscriptions, the highest rate among the three leading assistants.
Downloads and consumer spending keep rising
Sensor Tower estimates global AI app downloads will reach 2.3 billion in the first half of 2026, while user spending will top $4.2 billion. That compares with $1.83 billion in the same period of 2025. Growth is still strong, though both download and spending expansion are slowing, which the firm views as a sign of a maturing market.
Regionally, Asia posted a 3.3% drop in downloads in the first quarter of 2026, mainly due to weakness in China and India, but it still led the world in total downloads. Spending per user remains lower than in North America and Europe, a factor that could shape where AI companies prioritize paid feature rollouts.
OpenAI tests advertising inside ChatGPT
OpenAI is also broadening monetization beyond subscriptions. Sensor Tower said ChatGPT began testing ads in February, and by May an average of 17% of daily active users were seeing them. Software and shopping made up the largest ad categories, followed by media, entertainment and dining.
As shopping integrations expand inside ChatGPT, referral traffic has shifted away from Amazon toward Target, Walmart and Costco after Amazon blocked ChatGPT's crawler. Retail platforms are pushing their own built-in assistants as well. Walmart has rolled out Spark to help shoppers find products, while Amazon's Rufus has seen flat user growth but longer in-app time and higher conversion among people who use it.