Watching programmes on a TV set is still the most popular way for UK audiences to watch television - but streaming is catching up.
Traditional viewing - including catch-up within 28 days - still accounts for most TV watching, with an average of three hours and 12 minutes per day.
But according to Ofcom's latest Media Nations report, this marks a drop of 11 minutes since 2017.
Average daily viewing of streaming services rose last year to 26 minutes.
The number of UK households signed up to the most popular streaming platforms - Netflix, Amazon Prime Video, Now TV and Disney Life - increased from 11.2m (39%) in 2018 to 13.3m (47%) in 2019.
The total number of UK streaming subscriptions rose by a quarter in 2018 - from 15.6m to 19.1m - with many homes signing up to more than one service.
The report found that two in five of UK adults now consider online video services to be their main way of watching TV and film.
Despite traditional TV viewing declining, the five main public service broadcasters - BBC One, BBC Two, Channel 4, ITV/STV and Channel 5 - held their share of viewing, at 52%.
But viewers now watch 50 minutes less traditional TV each day than in 2010 - and those in the younger age bracket (16 to 24) have halved the time they spend watching TV that way during the same period.
This is the second Media Nations report to be published by Ofcom.
The first, which came out in 2018, found that Friends topped a list of the UK's most popular shows on paid-for streaming services.
It was the same again this year, with Friends at number one and accounting for around 2% of total streams.
The US sitcom, which first aired in 1994, was added to Netflix early last year.
Amazon's car show Grand Tour was the second most streamed, followed by You, The Good Place and Brooklyn Nine-Nine, which are all on Netflix.
BBC One's Line of Duty is the most-watched programme overall this year so far with 12.1 million tuning in to the final episode.
The channel's Bodyguard was the most-watched drama in 2018, with 14.3 million viewers for its final outing.
Yih-Choung Teh, strategy and research group director at Ofcom, said: "The way we watch TV is changing faster than ever before. In the space of seven years, streaming services have grown from nothing to reach nearly half of British homes.
"But traditional broadcasters still have a vital role to play, producing the kind of brilliant UK programmes that overseas tech giants struggle to match.
"We want to sustain that content for future generations, so we're leading a nationwide debate on the future of public service broadcasting."