Meta Platforms' Twitter rival Threads crossed 100 million sign-ups within five days of launch, CEO Mark Zuckerberg said Monday, dethroning ChatGPT as the fastest-growing online platform to hit the milestone.

Threads has been setting records for user growth since its launch Wednesday, with celebrities, politicians and other newsmakers joining the platform that is seen by analysts as the first serious threat to the Elon Musk-owned microblogging app.

"That's mostly organic demand, and we haven't even turned on many promotions yet," Zuckerberg said in a Threads post announcing the milestone.