Nearly three and a half years after ChatGPT first launched, AI assistants have become a daily tool for millions around the globe, and the competitive landscape is evolving rapidly. Although OpenAI’s chatbot remains the most popular assistant worldwide, its market share has slipped below 50% for the first time as users increasingly explore alternatives like Google’s Gemini, Anthropic’s Claude, and xAI’s Grok, according to analytics firm Sensor Tower’s State of AI Report for 2026. ChatGPT’s growth has been remarkable—it became the fastest app ever to reach 1 billion monthly users, as Sensor Tower reported this month. Notably, OpenAI tracks weekly active users and last reported 900 million of them in February. The chatbot still leads globally with over 1.1 billion monthly users, followed by Gemini with 662 million and Claude with 245 million.

Until January, ChatGPT held more than 50% of the market, but by the end of May, that share had dropped to 46.4%, driven by the rise of Gemini (27.7%) and Claude (10.3%). Other assistants—including Grok, Perplexity, DeepSeek, and Meta AI—each hold less than 5% of the market.

Sensor Tower’s report also reveals that users are becoming more willing to switch between assistants, with specific events accelerating this behavior. For instance, OpenAI’s deal with the U.S. Department of Defense in February triggered a noticeable spike in uninstalls, suggesting that brand trust and values alignment matter to users as much as features. While Gemini’s momentum largely stems from its integration with Google’s broader ecosystem, Anthropic’s Claude has built a strong reputation for productivity and is closing the gap on ChatGPT’s user-retention rate. In the first half of 2026, people are on track to download nearly 2.3 billion AI apps and spend over $4.2 billion on them, according to Sensor Tower estimates. That compares to $1.83 billion in spending during H1 2025—a surge indicating the industry is shifting focus from pure growth toward monetization. However, both download and spend growth rates have slowed, suggesting the market may be maturing even as absolute numbers climb. Regionally, Asia saw its first download decline of 3.3% in Q1 2026, driven by dips in China and India. Despite leading globally in total downloads, Asia trails North America and Europe in in-app spending—a divide that matters for companies deciding where to invest in premium features and monetization.

In the U.S., users are gravitating toward AI assistants for productivity tasks and spending more on premium features. Across platforms, average revenue per user has grown industry-wide, but Claude stands out. Thirteen percent of Anthropic’s users pay for a subscription—a conversion rate that leads the field and will be a key metric for investors evaluating which AI businesses are building lasting revenue. Sensor Tower estimates that time spent on AI apps will jump from 17.2 billion hours in H1 2025 to roughly 36 billion hours in H1 2026. The top three assistants command 89% of all time spent on AI assistant apps. Meanwhile, adjacent categories like AI companions or AI content-generation apps remain fragmented and wide open to competition, presenting both risks and opportunities depending on which players move first.

On the ads and shopping front, OpenAI began experimenting with ads in ChatGPT in February. According to Sensor Tower, the company has gradually increased the number of ads and the share of users who see them. By May, an average of 17% of daily users were being served ads—a number to watch as ChatGPT’s monetization strategy evolves beyond subscriptions.

Software and shopping are the largest advertiser categories in ChatGPT so far, followed by media and entertainment, and food and dining. As ChatGPT deepens its shopping integrations, it is increasingly sending referral traffic to retailers like Target, Walmart, and Costco. Amazon, which has blocked ChatGPT’s web crawlers, has seen stagnant referral traffic from the platform as a result, creating an opening for others. Sites like Walmart have embedded their own AI assistants to help shoppers find products. While Amazon’s Rufus has seen flat user growth, Walmart’s Spark has been gaining ground. Sensor Tower also noted that Amazon shoppers who used Rufus spent more time in the app and converted at higher rates than those who didn’t, hinting that on-platform AI can meaningfully influence purchasing behavior when users actually engage with it.