OpenAI’s chatbot ChatGPT has reached 800 million weekly active users. CEO Sam Altman announced the new milestone during the company’s developer conference, Dev Day. Rebecca Bellan reports for TechCrunch that this marks a significant increase in adoption. The user base has grown from 500 million weekly users at the end of March and 700 million in August. Altman also said that four million developers are building with OpenAI’s technology.