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...
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