TikTok is starting to go dark in the US

“Sorry, TikTok is not available right now,” the message read.

Hours before a federal law banning TikTok from the United States was set to take effect on Sunday, the Chinese-owned social media app went dark and American users could no longer access videos on the platform. Instead, the app greeted them with a message saying “a law banning TikTok has been passed.”

“We are fortunate that President Trump has indicated that he will work with us on a solution,” the message read. “Please keep an eye out!”

TikTok also appeared to have been removed from Apple and Google’s US app stores, some users said. In addition, TikTok’s sister app, Lemon8, stopped working and showed US users a message saying it is “not available right now.” Both TikTok and Lemon8 are owned by ByteDance, a Chinese internet giant.

TikTok became unavailable after the Supreme Court’s decision on Friday to uphold the law, which requires ByteDance to sell the app by Sunday or otherwise face a ban. The law was overwhelmingly passed by Congress last year and signed into law by President Biden. TikTok, which has faced national security concerns because of its Chinese ties, had thought it could win its legal challenge to the law, but failed.

The blackout capped a chaotic stretch for TikTok, which had made last-minute pleas to both the Biden administration and President-elect Donald J. Trump for a way out of the law. Until Saturday night, no one — including the U.S. government — was quite sure what would happen to it once the law took effect. The US has never blocked an app used by tens of millions of Americans essentially overnight.

The law has a provision to penalize app store operators like Apple and Google and internet hosting companies like Oracle for distributing or maintaining the TikTok app. Under the law, these companies face penalties as high as $5,000 per user who can access the app.

TikTok, Apple and Oracle did not immediately respond to requests for comment. Google declined to comment.

For TikTok and ByteDance, the development is a big blow. TikTok has around 170 million US users, who are some of the app’s most lucrative customers. In legal filings, TikTok has said that even a temporary disappearance could see users and creators leave for other platforms and never return, even if a ban were lifted.

The situation was further complicated by the fact that the law’s start date fell in the last days of Mr. Biden’s presidency. A White House spokeswoman suggested Saturday that the Biden administration would not begin fining companies on Sunday.

“We see no reason for TikTok or other companies to take action in the next few days before the Trump administration takes office on Monday,” White House press secretary Karine Jean-Pierre said in a statement. “We have made our position clear and straightforward: actions to implement this law will fall to the next administration.”

Spokesmen for the White House and the Justice Department did not respond to requests for comment after TikTok went offline.

Mr. Trump said Saturday that he would “most likely” find a way to give TikTok a 90-day extension when he takes office on Monday. The law allows the president to extend the deadline for a sale only if there is “significant progress” toward a deal that would put TikTok in the hands of a non-Chinese owner. It was not clear how that extension might work if the ban was already in effect.

Mr. Trump has also indicated that he could sign an executive order to circumvent the ban on the app. TikTok CEO Shou Chew is expected to attend the Mr. Trump’s inauguration on Monday.

On Saturday, the mood was gloomy on TikTok. Alix Earle, a content creator with 7.2 million followers who rise to fame on the app in 2022posted tearful videos mourning the platform.

“I feel like I’m going through heartbreak,” Ms. Earle wrote in one video. “This platform is more than an app or a job for me. I have so many memories in here. I’ve written every day for the last 6 years of my life. I’ve shared my friends, family, relationships, personal struggles, secrets. “

Other users used their last moment on the app to recreate viral dances. The “For You” page filled with montages of users’ favorite trends and songs, many dating back to the early days of the pandemic when the app rose in popularity.

At 9:00 PM Eastern on Saturday night, TikTok showed US users a pop-up message saying the app would soon stop working.

It said the law would “force us to make our services temporarily unavailable.” Soon after, TikTok went dark.

Late Saturday night, Ms. Earle found solace in appearing on a rival social media platform: Instagram.

“I just didn’t expect it this Saturday night,” she said of what happened to TikTok when she live-streamed on Instagram. RedNote, a Chinese video app that has become popular in recent days, would not be a long-term replacement, she said.

“We’re just going to have to make it a little more fun here, I think,” she said of Instagram.

On Sunday morning in China, TikTok’s announcement to US users that it would suspend the service was a trending topic on Weibo, a popular social media platform similar to X.

“This is a dark moment in the development of the Internet,” Hu Xijin, a former editor-in-chief of the state-run Global Times, wrote on Weibo. The US had set an example for “the entire Western world” to silence voices online in the name of national security, he wrote.

Diao Daming, a professor of international relations at Renmin University of China, called TikTok “the first big test Trump 2.0 will face.” Mr. Trump’s actions on TikTok could test his relationship with “China hawks” in Washington, Mr. Diao in a comment published on state media.

Claire Fu contributed reporting from Seoul. Nico Grant and Tripp Mickle contributed reporting from San Francisco. David McCabe contributed reporting from Washington.