More than three and a half years after ChatGPT’s initial release, AI assistants are now used by millions of people worldwide, and the competitive landscape is changing fast. While OpenAI’s chatbot is still the most popular assistant globally, its market share has dipped below 50% for the first time as users are migrating between different assistants 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 impressive. It became the fastest app ever to reach 1 billion monthly users, as Sensor Tower reported this month. Notably, OpenAI counts weekly active users, and it last reported 900 million of them in February. The chatbot still remains the most popular AI assistant worldwide with over 1.1 billion monthly users, followed by Gemini with 662 million and Claude with 245 million.
Until January, ChatGPT commanded over 50% market share, but by May’s end, it had fallen to 46.4% thanks to the rise of Gemini (27.7%) and Claude (10.3%). Other assistants, including 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 between assistants. Specific events appear to accelerate that behavior: OpenAI’s deal with the U.S. Department of Defense (DoD) in February triggered a measurable spike in uninstalls, for example — suggesting brand trust and values alignment matter to users, not just features.
Sensor Tower estimates that the hours spent on AI apps will have increased from 17.2 billion hours in H1 2025 to roughly 36 billion hours in H1 2026. The top three assistants command 89% time spent on AI assistant apps. Meanwhile, adjacent categories like AI companions or AI content-generation apps remain fragmented and wide open to competition, which represents both a risk and an opportunity depending on which players move first.
Source: techcrunch
