While TikTok remains hugely popular in Brazil, Indonesia and other markets, its 170 million users in the United States are its most valuable.

The app’s availability in the U.S. has been thrown into jeopardy over data privacy and national security concerns.

Disappointment, denial and confusion flooded US TikTok upon hearing that Chinese owner ByteDance planned to shut off the app by Sunday.

Kevin O’Leary’s $20B TikTok offer is rejected as ByteDance confirms it won’t sell the key technology behind the app’s success.

TikTok's U.S. ban arrived earlier than expected, logging users out abruptly on Saturday night before midnight ET. See how users are reacting to the sudden shutdown.

TikTok's app was removed from prominent app stores on Saturday evening just before a federal law that bans the popular social media platform went into effect.

Challenges came in tandem with TikTok’s success. U.S. officials expressed concerns about the company’s roots and ownership, pointing to laws in China that require Chinese companies to hand over data requested by the government. Another concern became the proprietary algorithm that populates what users see on the app.

TikTok faced a sudden shutdown in the U.S. due to a law taking effect, impacting 170 million Americans. President-elect Trump hinted at a reprieve, while the app's ownership ties to China's ByteDance sparked national security concerns.

The app had more than 170 million monthly users in the U.S. The black-out is the result of a law forcing the service offline unless it sheds its ties to ByteDance, its China-based parent company.

TikTok was not available for many of its 170 million users in the U.S. hours before a ban on the popular social media platform was supposed to officially go into effect. TikTok greeted some users opening the app Saturday night with the message,

Business moguls should be prepared to spend tens of billions of dollars for TikTok’s U.S. operations should parent company ByteDance decide to sell.