Most American teenagers use their phones to access the Internet, with one-fourth of them going online mostly on their mobile device, a survey showed Wednesday.

Some 78 percent of US teens have a cell phone, and 47 percent of those own smartphones, according to the survey by the Pew Internet Project with Harvard's Berkman Center for Internet & Society.

It found 74 percent of teens have mobile Internet access and one in four are "cell-mostly" Internet users, more than the 15 percent of the adult population in this category who go online without a desktop or laptop computer.

Fully 95 percent of teens are online, a percentage that has been consistent since 2006, the researchers found. But the patterns of Internet use have changed as more users go mobile.

"In many ways, teens represent the leading edge of mobile connectivity, and the patterns of their technology use often signal future changes in the adult population," the researchers wrote.

"Teens are just as likely to have a cell phone as they are to have a desktop or laptop computer. And increasingly these phones are affording teens always-on, mobile access to the Internet -- in some cases, serving as their primary point of access."

Tablets are also gaining ground, with 23 percent having access to one of these devices, the survey found.

The research, which interviewed some 800 parents and 800 youth from the ages of 12-17, found that teen girls are especially likely to be cell-mostly Internet users: 34 percent, compared with 24 percent of boys ages 14-17.