Meta founder and chief executive Mark Zuckerberg celebrated as the company's Threads platform passed 400 million active users, closing the gap on Elon Musk's X.
Various estimates indicate that X, which went live in 2006 as Twitter, has between 500 million and 600 million active monthly users.
"Threads on the up and up," Mr Zuckerberg posted on the platform with a fire emoji.
Adam Mosseri, who leads Meta's Instagram app and briefly oversaw Threads, also hailed the news.
"This started as a zany idea to compete with Twitter and has evolved into a meaningful platform that fosters the open exchange of perspectives," Mr Mosseri wrote.
He said those at Meta working on Threads know there is more work to be done to keep the user base growing. b
"I'm grateful to all of you for making this place what it is today," Mr Mosseri said.
Meta hastened the development of Threads in 2023 and launched it shortly after Elon Musk's acquisition of Twitter caused significant concern and controversy among users who worried about the world's richest person withdrawing various fact-checking and hate speech policies, among other changes.
In the initial description for the app on Apple iOS App Store, Meta said it wanted Threads to be a place “where communities come together to discuss everything from the topics you care about today to what you'll care about tomorrow”.
Because the app was paired heavily with Meta's Instagram accounts, it was quickly able to accumulate 100 million users in its first week, alengagement time on the app initially struggled to grow.
The similarity of Threads to X at the time prompted Mr Musk's company to send a letter to Meta alleging “wilful and unlawful misappropriation of Twitter's trade secrets and other intellectual property”. But there was no specific litigation.
The decision by Meta to pair the app with Instagram and make the sign-up process significantly easier increased interest in the platform. But it also caused scrutiny in countries such as Turkey, where regulators accused the app of breaching data-sharing policies due to its tie-in with Instagram.
Meta also later made tweaks to Threads to comply with data-sharing rules, among other policies in the EU.
While there is still much debate over how much time users are spending on Threads, it has managed to provide an alternative to X, which continues to operate under a cloud of scrutiny due to Mr Musk's recent forays into politics.
