The Supreme Court will hear arguments on Friday on the fate of TikTok, the enormously popular video app that Congress says poses a looming threat to the nation’s security.

Unless the justices intervene before a Jan. 19 deadline set by a federal law, the app must be sold or shut down.

The law, enacted in April with broad bipartisan support, said urgent measures were needed because TikTok’s corporate parent, ByteDance, was effectively controlled by the Chinese government, which could use the app to harvest sensitive information about Americans and to spread covert disinformation.

Saying that the law violates both its First Amendment rights and those of its 170 million American users, TikTok has urged the court to strike down the law.

The court has put the case on an exceptionally fast track, and it is likely to rule by the end of next week. Its decision will be among the most consequential of the digital age, as TikTok has become a cultural phenomenon powered by a sophisticated algorithm that provides entertainment and information touching on nearly every facet of American life.

“Americans use TikTok to communicate about all manner of topics — from culture and sports, to politics and law, to commerce and humor,” lawyers for the app told the justices. “For instance, people of diverse faiths use TikTok to discuss their beliefs with others. Recovering alcoholics and individuals with rare diseases form support groups. Many also use the platform to share videos about products, businesses and travel.”