Meta Platforms Inc.’s answer to Twitter has rocketed to 100 million users in less than a week, Chief Executive Officer Mark Zuckerberg announced on Monday.

“Threads reached 100 million sign ups over the weekend,” Zuckerberg said in a post. “That’s mostly organic demand and we haven’t even turned on many promotions yet. Can’t believe it’s only been 5 days!”

The Threads app, a spinoff from Instagram that uses people’s accounts for that service, got off to a scorching start on Wednesday and racked up 70 million users within two days, going “way beyond our expectations,” according to Zuckerberg.

Read More: Threads to Add $8 Billion to Meta Annual Revenue by 2025, Analyst Says

It’s still early days, but Threads, could generate some serious cash for the social media giant, according to Evercore ISI.

Threads will reach close to 200 million daily active users and generate about $8 billion in annual revenue over next two years, Evercore ISI analysts led by Mark Mahaney estimate.

The text-centric service closely resembles Twitter in look and functionality, earning the displeasure of Twitter owner Elon Musk who has accused it of being a copycat and an “Instagram minus pics.” The two billionaire owners have traded jibes in recent weeks and Threads is now at the center of an intensifying rivalry.

The new app’s launch has benefited from Meta’s immense reach — Instagram alone has more than a billion regular users — and changes at Twitter that have alienated large swathes of its most active user base. Threads still lacks a number of basic features, such as a chronological feed composed solely of people you choose to follow, but it provides a very familiar experience and doesn’t yet have any advertising.