The US government has issued an ultimatum to the Chinese owners of the popular video-sharing app TikTok, demanding they sell their stake in the app or face a US ban. Internal data from the app suggests that the number of monthly active users in the US has jumped by 50% in the past three years, with 100 million people now using the app regularly. The Biden administration is now following in the footsteps of the Trump administration in its attempt to rein in the app, and the response to the ultimatum and the testimony of TikTok's CEO will be closely watched.