More than three and a half years after the initial release of ChatGPT, the AI assistant is now used by millions of people around the world, and the competitive landscape is rapidly changing. OpenAI’s chatbot remains the world’s most popular assistant, but its market share has fallen below 50% for the first time as users migrate between different assistants such as Google’s Gemini, Anthropic’s Claude, and xAI’s Grok, according to analytics firm Sensor Tower’s 2026 State of AI report.
ChatGPT’s growth has been impressive. As Sensor Tower reported this month, the app became the fastest app in history to reach 1 billion monthly users. Notably, OpenAI counts weekly active users and last reported 900 million of them in February. Chatbots remain the most popular AI assistants around the world, with over 1.1 billion monthly users, followed by Gemini with 662 million and Claude with 245 million.
Until January, ChatGPT boasted a market share of over 50%, but by the end of May, the share had dropped to 46.4% due to the rise of Gemini (27.7%) and Claude (10.3%). Other assistants like Grok, Perplexity, DeepSeek, and Meta AI have less than 5% market share.
Sensor Tower’s State of AI Report also found that users are increasingly willing to switch assistants. Certain events seem to be accelerating that behavior. The February agreement between OpenAI and the US Department of Defense (DoD), for example, led to a measurable spike in uninstalls, suggesting that brand trust and value alignment are important to users, not just functionality. While Gemini’s momentum is largely due to its integration with Google’s broader tool ecosystem, Anthropic’s Claude has earned strong marks for productivity use cases and is closing in on ChatGPT’s user retention.
Sensor Tower estimates that in the first half of 2026, people will download nearly 2.3 billion AI apps and spend more than $4.2 billion on them. By comparison, spending in the first half of 2025 was $1.83 billion. This suggests that the industry is shifting its focus from pure growth to monetization. That said, download rates and spending growth rates are both slowing, indicating that the market may be maturing even as absolute numbers increase.
Regionally, Asia recorded a download decline of 3.3% for the first time in Q1 2026, driven by declines in China and India. Despite Asia leading the world in total downloads, it lags behind North America and Europe in terms of in-app spending. This difference is an important issue for companies deciding where to invest in premium features and monetization.
In the US, users are gravitating towards AI assistants for productivity tasks and are increasing their spending on premium features. Across platforms, average revenue per user is increasing across the industry, but Claude stands out. Thirteen percent of Anthropic users pay for a subscription plan. This conversion rate leads the sector and is a noteworthy metric for investors evaluating which AI businesses are building sustainable returns.
Sensor Tower estimates that time spent on AI apps will increase from 17.2 billion hours in the first half of 2025 to approximately 36 billion hours in the first half of 2026. The top three assistants account for 89% of the time spent in AI assistant apps. Meanwhile, adjacent categories such as AI companions and AI content generation apps remain fragmented and highly competitive, presenting both risks and opportunities depending on which player makes the first move.
OpenAI began experimenting with ads on ChatGPT in February. Sensor Tower says it has gradually expanded the number of ads and the percentage of users who see them. By May, ads were being served to an average of 17% of users each day. This number is noteworthy as ChatGPT’s monetization strategy evolves beyond subscriptions.
So far, the largest advertiser category on ChatGPT is software and shopping, followed by media and entertainment and food and dining.
As ChatGPT strengthens its shopping integrations, it is increasingly sending referral traffic to retailers like Target, Walmart, and Costco. Amazon has blocked ChatGPT’s web crawler, resulting in stagnant referral traffic from the platform.
That gives others an opening. Sites like Walmart are incorporating their own AI assistants to help shoppers find products. Amazon’s Rufus has seen flat user growth, while Walmart’s Spark is gaining momentum. Sensor Tower also noted that Amazon shoppers who used Rufus spent more time in the app and had higher conversion rates than those who didn’t, suggesting that AI on the platform can have a meaningful impact on the purchasing behavior of users when they actually use it.
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