By Rebecca Heilweil

While Congress probes Facebook as part of a broader, antitrust investigation of social media sites and other tech giants, it's the universe of the video game Fortnite ー released in 2017 by Epic Games ー that could become the most popular social platform among tweens and teens, according to new data from the National Research Group.

The market researcher found that among the 10- to 17-year-olds who play Fortnite at least once a week, playing or perusing its accounts for a quarter of their free time.

"Among all the entertainment platforms, Fortnite is ranked number two in 'brands I love' among teens," NRG CEO Jon Penn told Cheddar.

The game also had the highest reported usage among tweens ー those 10 to 12 years old ー this year over last year, more than Netflix ($NFLX), Facebook($FB), or YouTube.

"Why is that? For us, the key headline is that 85 percent of 10- to 17-year-olds say playing Fornite is having a positive impact on my life. And when you look at all the social media platforms together, the highest any of them get is 64 percent."

"Fortnite is building on all the promises that social media set out to do," said Penn. He argued that game and platform have helped young people build self-confidence, find a safe place from bullying, and invent their "authentic" selves.

Fortnite's popularity could spell trouble for both streaming companies and social media sites that compete for young peoples' attention. Penn pointed out that the platform managed to attract 10 million simultaneous viewers to its DJ Marshmello concert in February.

This January, Netflix said in [an earnings report for 2018] ( that it faces more of a threat from Fortnite than it does from Hulu or HBO.

"Free time is finite," said Penn. "Particularly, when you're looking at 10- to 17-year-olds, what they're looking for is a safe place where they can be themselves." He argues that Fortnite builds community, and, through avatars, provides people an avenue for self-expression.

"You can try on new identities," he said. "This active play, and creating in a safe place, is something that's new, and is a threat against other platforms."

"They're talking to their friends in a deep way that they're not on social media," Penn added. "We're also finding it to be a great communications medium."