The Pew Research Center report confirms a trend seen in other surveys, showing a sharp drop in Facebook's share of what had long been a core age segment for the huge social network.

The survey found 51 percent of US teens ages 13 to 17 use Facebook, compared with 85 percent for YouTube, 72 percent for Instagram and 69 percent who are on Snapchat.

The landscape has shifted since a 2014-15 Pew survey which found Facebook leading other social networks with 71 percent of the teen segment.

According to the survey, 95 percent of the teens survey said they used a smartphone and 45 percent were online "almost constantly," with both figures showing increases from prior surveys.

"The social media environment among teens is quite different from what it was just three years ago," said Pew researcher Monica Anderson, the lead author of the report.