Google's Gemini AI assistant is rapidly closing the gap with ChatGPT in user growth, according to 2025 data from Sensor Tower. While ChatGPT still holds 55% of the global monthly AI chatbot user base and 50% of mobile downloads, Gemini's monthly users surged by 30% between August and November 2025, compared to ChatGPT's modest 6% increase. Gemini's engagement time also saw a significant 120% rise, driven by innovative features like the Nano Banana image-generation tool. In response, OpenAI is implementing internal strategies to address the growing competition.