Meta has officially launched its surprisingly popular Twitter alternative, Threads—shocking even Mark Zuckerberg as sign-ups hit 30 million within the first 24 hours. Though a separate app, Threads is built as a convenient extension of Instagram, requiring an Instagram account to join and allowing users to port their entire Instagram following over in one click. That has clearly made Threads appealing to a huge chunk of Instagram users.

“We didn’t expect tens of millions of people to sign up in one day, but supporting that is a champagne problem,” Instagram CEO Adam Mosseri said in a cheery update on Thursday.