“Sorry, TikTok isn’t available right now,” the message read.

Hours before a federal law banning TikTok from the United States was set to take effect, the social media app went dark, and U.S. users could no longer access videos on the platform. Instead, the app greeted them with a message that said “a law banning TikTok has been enacted.”

“We are fortunate that President Trump has indicated that he will work with us on a solution,” the message said. “Please stay tuned!”

The app also appeared to have been removed from Apple’s U.S. app store, some users said.

TikTok became unavailable after the Supreme Court decision on Friday upholding the law, which calls for TikTok’s Chinese owner ByteDance to sell the app by Sunday or otherwise face a ban. The law had overwhelmingly passed Congress last year and been signed by President Biden. TikTok, which has faced national security concerns for its Chinese ties, had expected to 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 entirely sure what would happen to it when the law took effect. The United States 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, those companies face penalties as high as $5,000 per user who can access the app.

For TikTok and ByteDance, the developments are a major blow. TikTok has roughly 170 million users in the United States, who are some of the app’s most lucrative customers. In legal filings, TikTok has said that even a temporary disappearance could kneecap it, with users and creators leaving for other platforms and never returning even if a ban was lifted.

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