In this photo illustration, the ChatGPT (OpenAI) logo is displayed on a smartphone screen.Sopa Images/Getty Images ChatGPT may be the fastest-growing app in history with 100 million users after just over two months. A UBS report showed that it took TikTok over nine months to reach the same number of people. OpenAI is rolling out a $20-a-month subscription to ChatGPT for easy access and faster responses. ChatGPT may have become the fastest-growing app in history after it was estimated to have reached 100 million monthly active users, or MAUs, by the end of January, a report by Swiss banking giant UBS said.The OpenAI-owned chatbot has surpassed 100 million MAUs just over two months after its launch — comfortably beating the growth speeds of major apps like TikTok and Instagram, according to the UBS note, which Insider has viewed.It took TikTok nine months to reach the same level of users; Instagram took two and half years; and Spotify only amassed 100 million MAUs after four and a half years, the report said, citing data from data analytics firm Similar Web.