The online video boom is starting to eat into TV viewing time, an ICM survey of 2,070 people for the BBC suggests.
Some 43% of Britons who watch video from the internet or on a mobile device at least once a week said they watched less normal TV as a result.
And online and mobile viewing is rising - three quarters of users said they now watched more than they did a year ago.
But online video viewers are still in the minority, with just 9% of the population saying they do it regularly.
Another 13% said they watched occasionally, while a further 10% said they expected to start in the coming year.