According to analytics firm Sensor Tower’s 2026 State of AI Report, ChatGPT’s share of global AI assistant monthly active users fell to 46.4% by end of May — the first time it has dipped below 50% since launch. The chatbot remains the most-used AI assistant with over 1.1 billion monthly users, but Gemini has closed ground sharply to 662 million (27.7% share) and Claude has reached 245 million (10.3% share). Grok, Perplexity, DeepSeek, and Meta AI each hold less than 5%. ChatGPT had maintained above-50% share through January 2026. Sensor Tower also noted that 13% of Anthropic’s users pay for a subscription — the highest conversion rate in the industry — while OpenAI began testing ads in ChatGPT in February, with roughly 17% of daily users being served ads by May. User switching behaviour has accelerated, with specific events acting as catalysts: ChatGPT uninstalls surged 295% after OpenAI announced a U.S. Department of Defense deal in February.
The broader AI app market is expanding but maturing. Sensor Tower estimates users are on pace to download 2.3 billion AI apps in H1 2026 and spend over $4.2 billion on them, up from $1.83 billion in H1 2025 — though both download and spend growth rates are decelerating. Time spent on AI apps is estimated to nearly double year over year, from 17.2 billion hours in H1 2025 to roughly 36 billion hours in H1 2026, with the top three assistants commanding 89% of that time. Asia recorded its first quarterly download decline in Q1 2026, down 3.3%, driven by dips in China and India, while North America and Europe lead on in-app spending. Gemini’s growth is largely attributed to its integration with Google’s broader ecosystem; Claude’s gains are driven by productivity use cases and, notably, user retention that is approaching ChatGPT’s rate.