ChatGPT remains the world’s largest AI assistant, but its market grip is weakening as rivals gain ground, according to Sensor Tower’s State of AI 2026 report.

The report found that ChatGPT’s share of the global AI assistant market fell below 50% for the first time this year. After controlling more than half the market until January, its share dropped to 46.4% by the end of May. Google’s Gemini reached 27.7%, while Anthropic’s Claude climbed to 10.3%.

The decline comes even as ChatGPT’s user base continues to grow. Sensor Tower estimates the platform now has more than 1.1 billion monthly active users, making it the fastest mobile app to reach the one-billion-user mark. Gemini follows with 662 million monthly users and Claude with 245 million.

Users increasingly switch platforms: The report suggests users are increasingly willing to switch between AI assistants. Sensor Tower noted that uninstallations of ChatGPT in the US spiked after OpenAI announced a partnership with the US Department of Defense, while Claude’s downloads surged during the same period. Claude’s US audience share has risen from 4.4% to nearly 14% over the past year, with its global audience growing 452% year-on-year in May.

While competition is increasing, the market remains highly concentrated. ChatGPT, Gemini and DeepSeek account for nearly 90% of total time spent on AI assistant apps. User engagement is also rising rapidly, with global time spent on generative AI apps projected to reach 36 billion hours in the first half of 2026, more than double the 17.2 billion hours recorded a year earlier.

AI spending continues to rise: Consumer spending on AI is growing as companies push subscriptions and premium features. Sensor Tower estimates AI apps will generate more than $4 billion in in-app revenue during the first half of 2026. However, download and spending growth rates have begun slowing, suggesting the market may be moving from rapid expansion toward maturity.

The report also highlights diverging regional trends. Asia, the largest market for AI app downloads, recorded a 3.3% decline in downloads during the first quarter of 2026, driven by slowdowns in China and India. North America and Europe, meanwhile, continue to lead in spending.

Claude leads in monetisation: Claude appears to be outperforming rivals in monetisation. According to Sensor Tower, 13% of Claude users pay for a subscription, the highest conversion rate among major AI assistants. In the US, Claude’s mobile average revenue per user rose from less than $0.50 in September 2025 to $2.76 in May 2026.

AI’s growing role in shopping and ads: Beyond chatbots, AI is increasingly influencing online shopping and advertising. Sensor Tower found that referral traffic from AI assistants to retail websites increased across all major retail categories between late 2024 and early 2026. Retailers such as Walmart and Target have seen AI-driven referrals account for more than 1.5% of visits, while Amazon has lagged due to its limited access to certain AI web crawlers.

Advertising is emerging as another revenue stream. ChatGPT began testing ads earlier this year and gradually expanded their reach. By May, around 17% of its daily users were being shown advertisements. Companies in software, shopping, travel and financial services were among the earliest advertisers on AI platforms.

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