By Aditya Soni and Jaspreet Singh

(Reuters) -Social media platform Bluesky is adding millions of users as people flee X after Donald Trump was elected U.S. President and as an upcoming change to the terms of service threatens to complicate legal challenges for the Elon Musk-owned platform.

Bluesky has gained about 2.5 million new users in the past week, raising its total users to more than 16 million, it said on Thursday. It is among a slew of apps looking to replace the platform formerly known as Twitter after Musk's takeover.

"We're seeing record-high activity levels across all different forms of engagement: likes, follows, new accounts, etc, and we're on track to add 1 million new users in one day alone," Bluesky said in a statement.

Several well-known organizations and personalities, including the nonprofit Center for Countering Digital Hate, British news publisher the Guardian and former CNN anchor Don Lemon have said they were leaving X due to concerns about the platform's content and the looming terms change.

X was called out by misinformation experts during the election for playing a central role in enabling the spread of false information about the critical battleground states.

On Nov. 6, as news broke that Musk ally Trump won the presidency, X attracted 46.5 million visits in the U.S. - more than any day in the past year and 38% higher than an average day in recent months, according to analytics firm SimilarWeb.

But more than 115,000 U.S. web visitors deactivated their X accounts - the most since Musk bought the platform, SimilarWeb data showed.

Bluesky's website, meanwhile, attracted around 1.2 million visitors on Nov.6, more than Meta Platforms-owned Threads, which had around 950,000 visitors. But Threads app had more visitors than that of Bluesky.

"Outsized growth, particularly for Bluesky, may have been driven by a rise of controversial content or technical issues on competitor X," said Abraham Yousef, senior insights analyst at market intelligence firm Sensor Tower.

"The departure of popular accounts, media personalities, or organizations, may have led consumers to conclude that X is no longer their preferred platform, which could also be fueling growth on other platforms, particularly Bluesky and Threads."

TERMS CHANGE

The Bluesky surge comes ahead of a change in X's terms on Friday that requires all legal disputes related to the platform to be brought exclusively in the U.S. District Court for the Northern District of Texas or state courts in Tarrant County, Texas.

The Center for Countering Digital Hate said on Thursday the change could hinder legal challenges against the platform by steering future lawsuits toward judges Musk believes "will be on his side".

"Now, the billionaire will be able to bring lawsuits to friendly courts against whoever disagrees with him on his platform," said the nonprofit that has faulted Musk for letting hate speech spread on X.

X and Musk did not respond to requests for comment.

Still, Bluesky's user count is much smaller than rivals. Threads has about 252 million monthly active users on its mobile app, while X has about 317 million, according to Sensor Tower.

"X seems to be in a better position than it has in a while given the ability to represent the views of president-elect Trump," said D.A. Davidson & Co analyst Gil Luria.

"While there are other competing platforms, those may have a hard time catching up with X, since microblogging has significant network effects."

(Reporting by Aditya Soni and Jaspreet Singh in Bengaluru; Additional reporting by Rishi Kant in Bengaluru; Editing by Arun Koyyur)