YouTube, Instagram, Snapchat and Facebook take over from TV as most popular kids' pastimes
An annual survey by research agency Childwise suggested young people now use the internet for three hours a day on average, compared with just 2.1 hours sitting in front of the television.
Video-sharing website YouTube, image-sharing sites Instagram and Snapchat and social network Facebook were among the most popular online destinations for children.
And half of the more than 2,000 five to 16-year-olds who took part in the survey had watched programmes on Netflix, ahead of ITV on 47% and BBC One on 46%.
The trend may have been aided by a surge in tablet ownership among children, which was up 50% on last year.
Simon Leggett, Childwise research director, said this year's survey showed that "TV viewing has been redefined".
He told the BBC: "Growing access to the internet at any time and in any place, and a blurring of television content across channels and devices, brings a landmark change in behaviour this year.
"Children are now seeking out the content of their choice. They still find traditional TV programmes engaging but are increasingly watching them online and on-demand or binge-watching box sets."