TikTok says it is bringing its services back to the United States less than 24 hours after the app went dark to comply with a national ban.
The app's future has become a headline political issue on the eve of Donald Trump's return to the presidency, and Trump has been promising to find a way to revive it.
"As of today, TikTok is back," Trump told his inauguration eve rally in Washington DC on Sunday evening, local time.
"We have no choice, we have to save it. A lot of jobs."
The president-elect has pledged to issue an executive order to delay the ban to negotiate a deal to keep it operating.
It's on a long list of orders Trump is expected to sign on day one of his presidency.
Others are likely to overturn environmental regulations, cancel diversity programs, lift bans on offshore oil and gas drilling, and pave the way for his "mass deportation" plan.
"You're going to see executive orders that are going to make you extremely happy," Trump told the rally.
He later added: "Somebody said yesterday, 'Sir, don't sign so many in one day, let's do it over a period of weeks.
"I said, 'Like hell we're going to do it over weeks. We're going to sign them at the beginning.'
Trump suggests US could buy half of TikTok
The night before Trump's rally, TikTok disappeared from app stores and blocked access for its 170 million American users to comply with a Sunday deadline for its shutdown.
But on Sunday morning, Trump promised to issue an executive order on Monday, after his inauguration, to extend the deadline for shutdown. That would provide time to "make a deal to protect our national security" and keep the app running in the US.
"I would like the United States to have a 50 per cent ownership position in a joint venture," Trump posted. "By doing this, we save TikTok, keep it in good hands and allow it to say [sic] up."
A few hours later, TikTok announced it was "in the process of restoring service".
"We thank President Trump for providing the necessary clarity and assurance to our service providers that they will face no penalties," a statement from the company said.
The US Congress passed a law, with bipartisan support, in April last year. It ordered TikTok's China-based parent company, ByteDance, to sell the app or face a ban.
Trump said last week he had spoken to Chinese President Xi Jinping about TikTok, among other topics.
Chinese Vice-President Han Zheng has travelled to the US for the inauguration. He met with vice-president-elect JD Vance on Sunday.
TikTok CEO Shou Chew has also reportedly been invited to Trump's inauguration, to sit with other VIPs from the tech industry.
They include X owner Elon Musk, who Trump has appointed to co-lead his cost-cutting operation, and Facebook owner Mark Zuckerberg, who pledged to cut fact-checking from the platform after meeting with Trump.
The TikTok ban legislation, which has survived a Supreme Court challenge, could make Trump's promise difficult to keep. Executive orders generally cannot override or reverse legislation passed by Congress.
Republican senator Tom Cotton responded to TikTok's announcement by warning that "any company that hosts, distributes, services, or otherwise facilitates communist-controlled TikTok could face hundreds of billions of dollars of ruinous liability under the law".
Trump had tried to ban the app during his first term as president, but in recent months has spoken favourably about the app.
"We'll have a look at TikTok," he said at his first post-election press conference.
"I have a warm spot in my heart for TikTok."
