The BBC is to screen Doctor Who's New Year special in 4K resolution and high dynamic range (HDR) colour via iPlayer.
When the programme is broadcast, viewers will be prompted to switch to the higher quality streamed version by pressing the red button. Ultra-High Definition will deliver four times as many pixels as HD video.
To take advantage of the facility, households will need a compatible TV and a relatively fast internet connection. The BBC recommends a minimum 24 megabits per second (Mbps) connection.
Other programmes available in UHD this Christmas include The Queen's Christmas Broadcast, Black Narcissus, Dynasties and A Perfect Planet.
A BBC spokesman said: "Many factors are taken into account when we're deciding what content to make available in UHD. We've made a range of drama, factual and natural history programmes available for iPlayer viewers to watch in UHD, as well as some of the biggest live events, and we'll continue to look at these as well as other areas as we explore UHD on iPlayer in the future."