WASHINGTON (AFP) - American teens think Facebook has definitely lost its cool factor, but use it as much as ever.

A survey released on Monday (Dec 7) by Forrester Research found 78 per cent of US teenagers use Facebook, a figure unchanged from last year.

That's more than any other "social" site except the video-sharing service YouTube, used by 80 per cent of teens.

The cool factor isn't there for the leading social network, Forrester found: 65 per cent of online users ages 12 to 17 say Facebook is cool, far less than services such as YouTube (80 per cent), Snapchat (79 per cent) and Facebook-owned Instagram (78 per cent).

"Sure, young people don't think Facebook is cool - but that doesn't mean they've stopped using it," the report said.

Forrester analysts said Facebook "generates more hyper-usage than any other social site", adding that a third of teen Facebook users say they are on the site "all the time", far more than any other social site.

"Facebook is a key way for young people to keep in touch with friends," they wrote.

The report said the billion-plus member social network can be an important tool for marketers who want to connect with young people, but they need to finetune their approach with tools such as "social relationship marketing" to build brand awareness and loyalty.

The research firm surveyed 4,485 teens ages 12 to 17 in April 2015. The margin of error was estimated at 1.5 percentage points.