A unanimous Supreme Court on Friday upheld a law that effectively bans the wildly popular app TikTok in the United States starting on Sunday. The ruling ended, at least for now, a legal battle involving national security, free speech and a cultural phenomenon that had millions of Americans deliriously swiping their phone screens at any given moment.

The ruling, which forces the app to go dark if it remains under Chinese control, could be a death blow to TikTok’s American operations. President-elect Donald J. Trump, who is to be inaugurated the following day, has vowed to “save” the app though his mechanisms for doing so remain unclear.

In ruling against TikTok, the court acknowledged the wide-ranging cultural impact of the app while siding with the government’s concerns that China’s role posed national security concerns.

“There is no doubt that, for more than 170 million Americans, TikTok offers a distinctive and expansive outlet for expression, means of engagement, and source of community,” the court’s opinion said. “But Congress has determined that divestiture is necessary to address its well-supported national security concerns regarding TikTok’s data collection practices and relationship with a foreign adversary.”

TikTok gained a foothold in American culture in 2020 as a pandemic curiosity and swiftly grew into an undeniable juggernaut. It serves up short-form videos that are a leading source of information and entertainment to tens of millions of Americans, especially younger ones.

Not only has the app given rise to a new crop of celebrities and fueled chart-topping books, music and movies, but it has also helped shape conversation around the Israel-Hamas war and last year’s U.S. presidential election.