TikTok’s days in the US could be numbered. The Supreme Court on Friday upheld a federal law that will effectively ban the social media app in the U.S. as of Jan. 19.

There are still a few ways TikTok could wriggle out of its do-or-die predicament. The app's parent company ByteDance has appealed to the incoming Trump administration to take some kind of action to save the platform. Trump has already said he'll "save" TikTok, but it's unclear exactly how the president-elect will put the brakes on an act of Congress, that's been upheld by The Supreme Court.

There's also uncertainty around just what happens when the clock strikes midnight on Jan. 19. TikTok has said it will go dark, but that's not quite what the law banning it calls for. Instead, it prohibits companies from hosting the service, which means it could still live on in some kind of app purgatory until Trump or Congress finds a way to reverse the ban.

But while TikTok's users are waiting with bated breath to see whether their favorite app dies off, the company's Silicon Valley rivals could be staring down a windfall are licking their chops at the prospect of bringing in TikTok's 170 million users and associated advertising dollars.

Meta and YouTube take on TikTok’s lost users

The biggest winner would also be one of TikTok’s long-term critics, Meta (META) CEO Mark Zuckerberg. In particular, Instagram could see a sizable uptick in advertiser dollars if TikTok bites the dust.

“In general, it’s a good thing for Meta,” William Blair research analyst Ralph Schackart told Yahoo Finance. “We estimate in a note potentially 60% to 70% of TikTok spend could move to Instagram and it monetizes at around 3x the rate of TikTok.”

Meta has been battling TikTok for years, with Zuckerberg at varying times raising the specter of Chinese technological dominance over the US and threats to free speech. Zuckerberg also rolled out Instagram and Facebook’s Reels feature, a short-form video offering similar to TikTok, to combat the rival service and bring users back to his platforms.

If TikTok closes up shop, users will undoubtedly flock to Meta’s apps, increasing the number of people using the services and the amount of time they spend on them — which in turn would drive increased advertising revenue.

YouTube and its Shorts platform should also gain from TikTok’s loss. According to Morgan Stanley managing director Brian Nowak, every 10% of the time users would have spent on TikTok that goes to YouTube would add $400 million to $750 million in ad revenue to the video platform’s sales.