This is not your father's Facebook. It's your grandfather's.
Data from the Pew Center for Internet and American Life released Monday show that Facebook's strongest growth over the last year has come from users over 65, as more older users sign onto the site to keep in touch with friends, children, and grandchildren.
The survey found that 45 percent of American seniors who use the Internet are on Facebook, up from 35 percent the previous year.
Use among teens, however, has stagnated at 84 percent. That's in keeping with a growing concern that Facebook is seeing lower engagement with the younger users that drove its early popularity, something that the company acknowledged in an earnings call this year.
Facebook may be a victim of its own success after nearly 10 years as the country's leading social network, said Pew senior researcher Aaron Smith.
"It's hard to get more than 85 percent of anyone doing anything," he said. "A lot of the easy converts in the younger group, or even in the older and middle-aged group, are already on the site. The senior group is the only area that has any substantial area for growth."
Facebook is seeing an uptick in teen use on Instagram, which it bought for $1 billion in 2012, indicating that it's far from being down for the count as a company.
Still, a stagnating teen audience - the percentage of those in the 18-29 age group that use the site fell two percentage points compared with last year - fits in with a recent study from researchers at University College London, which found some British teens leaving Facebook because of the influx of older users.
An ethnographic study of 16- to 18-year-olds north of London found teens opting to use private messaging services such as WhatsApp and Snapchat to communicate with their friends. In many cases, the study said, teens stay on Facebook at the behest of their parents, who have made it a tool for keeping track of their children.
"You just can't be young and free if you know your parents can access your every indiscretion," wrote Daniel Miller, a professor of Material Culture at University College, who ran the study.
In other words, teens are using Facebook, but not for the same reasons that they once did. And that, Smith said, fits in with a larger trend in social media: Americans are diversifying the social networks that they use.
More than 40 percent of Americans, Pew found, maintain multiple social network accounts for different purposes.
Facebook, which has more than one billion users and is used by 71 percent of Americans, seems to be the "default" social network, he said, while Pinterest skews more heavily to women, LinkedIn to more educated or wealthier users, and Twitter among young adults and African Americans.
"People are pretty utilitarian," Smith said. "This fits really well with a lot of the research we've seen in terms of how people navigate all of these things."
Users go to specific places based on what they're trying to do, Smith said, and so engagement for many of the smaller sites are on par with Facebook, Smith noted. Fifty-seven percent of Instagram users, for example, return daily to the site to check for updates, compared to 63 percent of Facebook users. Nearly half of Twitter's users, 46 percent, also make the site a daily habit.