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.

Full Sensor Tower report : ChatGPT’s market share fell to 46.4% at the end of May, as Gemini rose to 27.7% and Claude to 10.3%; Grok, Meta AI, and others have less than 5%.