PCs currently lead, but mobile second-screen use will soar this year.
The NPD Group says 425 million devices in US homes are connected to the internet, supporting a recent infographic that said there will be nine connected devices for every American man, woman, and child by 2016.
The computer is still the primary web-enabled device, but games consoles, Blu-ray players and connected TVs are becoming increasingly popular platform for web browsing.
Mobile devices are also hugely popular, with smartphones and tablets accounting for 133m and 31.8m devices respectively, while the second-screen trend (mobile use alongside TV viewing) is expected to rise throughout the year.
John Buffone, director, NPD’s Connected Intelligence, said: "Mobile is adding another dimension powered by screen sharing technologies that allows users to project their tablet or smartphone onto their TV.
"Through 2013, multi-screen and multi-device synergy will lead the growth in the broader connected device market, but only if services consumers desire are delivered in a simplistic manner. In this connected world, content providers and consumer technology OEMs need to determine the optimal mix of services and have them on the right devices."