Mark Zuckerberg and Elon Musk Were Once Ready to Fight. Now Meta Is Openly Copying X's Community Notes Algorithm. Meta is aiming to bring Community Notes to Facebook, Instagram, and Threads.

Mark Zuckerberg and Elon Musk were once poised to fight in a cage match in 2023, before Zuckerberg called it off, saying that Musk was "not serious." Now, the two billionaires have gone from the brink of battle to using each other's technology.

On Thursday, Meta stated that it will copy technology implemented by Musk's X to create its new content moderation tool Community Notes.

Community Notes will allow users on Facebook, Instagram, and Threads to give feedback on posts in the form of an explanation citing their sources. The notes must be less than 500 characters and include a supporting link. Community Notes aren't a new concept — X started using the system widely after Musk bought the company in the spring of 2022.

Meta will specifically tap into X's widely available and replicable open-source algorithm as the foundation of its own Community Notes feature, which it intends to begin testing in the U.S. on March 18.

Related: Meta Ends Fact-Checking Program, Replaces It With New System: 'We've Seen This Approach Work on X'

"As X's algorithm and program information is open source – meaning free and available for anyone to use – we can build on what X has done, learn from the researchers who have studied it, and improve the system for our own platforms," Meta wrote in a blog post. "As our own version develops, we may explore different or adjusted algorithms to support how Community Notes are ranked and rated."

^{Mark Zuckerberg (left) and Elon Musk (right). Photo by Mandel NGAN and Alain JOCARD / AFP}

Meta first announced in January that it would end its eight-year independent fact-checking program and transition to a Community Notes system. The company previously relied on experts at organizations like The Associated Press to determine whether its content was factually correct but said it was moving to Community Notes to allow for more people to monitor posts and add context.

Since January, about 200,000 users have signed up to volunteer as contributors to Community Notes across Facebook, Instagram, and Threads. Meta intends to slowly implement the program and eventually allow contributors to add Community Notes to posts from everyone from public figures to personal connections. The notes will be added anonymously and do not apply to ads.

Meta is copying X's Community Notes model, which has achieved some success. According to a study released in April 2024 by researchers at the University of California, San Diego, X's Community Notes were almost always accurate and cited high-quality sources.

Related: Meta Says It Has Fired 20 Employees For Leaking Information: 'We Expect There Will Be More'

While Zuckerberg may be tapping into the Community Notes algorithm Musk uses at X for Meta's algorithm, the road goes both ways: Musk too has expressed an interest in open-source technology created by Zuckerberg-led Meta.

In April 2024, Meta released Llama 3, its latest AI model that is free for anyone to download and use. That same month, Musk wrote in a post on X that the AI model was "not bad."

Not bad

— Elon Musk (@elonmusk) April 18, 2024

According to the Bloomberg Billionaires Index, Musk and Zuckerberg are among the top three richest people in the world, worth $319 billion and $219 billion respectively.