Twitter's rival has grown rapidly since its launch last Wednesday.
Mark Zuckerberg said the new app had reached 100 million users over the weekend. Instagram, owned by Zuckerberg's Meta empire, once took a week to reach 100,000 users when it launched as a standalone platform in 2010.
"Threads hit 100 million registrations over the weekend," Zuckerberg wrote. "This is mostly organic demand and we haven't activated many promotions yet. Can't believe it's only been five days!”
Threads users need an Instagram account to sign in to the new app. Posts on Threads can be 500 characters long, compared to 280 for most Twitter users, and videos of up to five minutes can be posted.