ChatGPT, the popular chatbot from OpenAI, is estimated to have reached 100 million monthly active users in January, just two months after launch, making it the fastest-growing consumer application in history, according to a UBS study on Wednesday. The report, citing data from analytics firm Similarweb, said an average of about 13 million unique visitors had used ChatGPT per day in January, more than double the levels of December. “In 20 years following the internet space, we cannot recall a faster ramp in a consumer internet app,” UBS analysts wrote in the note. It took TikTok about nine months after its global launch to reach 100 million users and Instagram 2-1/2 years, according to data from Sensor Tower. ChatGPT can generate articles, essays, jokes and even poetry in response to prompts. OpenAI, a private company backed by Microsoft Corp, made it available to the public for free in late November. On Thursday, OpenAI announced a $20 monthly subscription, initially for users in the United States only. It would provide a more stable and faster service as well as the opportunity to try new features first, the company said. Analysts believe the viral launch of ChatGPT will give OpenAI a first-mover advantage against other AI companies. The growing usage, while imposing substantial computing cost on OpenAI, has also provided valuable feedback to help train the chatbot’s responses.