Zenith, the ROI agency, predicts in its Online Video Forecasts 2017 study that global consumers will spend an average of 47.4 minutes a day watching videos online this year, up from 39.6 minutes in 2016.
There is expected to be a 35% increase in viewing on mobile devices (smartphones and tablets) to 28.8 minutes a day, while viewing on fixed devices (desktop PCs, laptops and smart TVs) will rise by just 2% to 18.6 minutes a day.
This shift towards mobile video viewing is expected to accelerate over the next couple of years, with Zenith forecasting that viewing on fixed devices will decline 1% in 2018 and 2% in 2019.
At the same time, mobile video viewing, which currently averages 29 minutes a day, is expected to grow 25% in 2018 and 29% in 2019, driven by the spread of mobile devices, improved displays and faster mobile data connections.
According to Zenith, which examined 63 key markets for this year's report, mobile devices will account for almost three-quarters (72%) of all online video viewing by 2019, up from 61% in 2017.
Zenith also examined how the rapid growth of video consumption around the world is also driving growth in online video advertising, which is expected to increase 23% in 2017 to $27.2bn, up from $22.2bn in 2016.
Looking at the UK market, where consumers are expected to watch an average of 53.3 minutes a day of online video this year, online video adspend is forecast to rise to £1.7bn.
Globally, online video is expected to account for almost a third (31%) of all digital display advertising by 2019, up from 28% in 2017 and 21% in 2012.
"Online video is one of the fastest-growing channels of advertising, triggering heavy demand from brands for high-quality content," said Jonathan Barnard, Head of Forecasting and Director of Global Intelligence at Zenith.
"Video platforms that can capture the attention of the most consumers with the best content will reap the highest rewards."
Data sourced from Zenith; additional content by WARC staff