YouTube

YouTube was a website on the Internet on Earth in the 21st century.

After a wave of Shakri cubes arrived on Earth, people posted about them on YouTube. (TV: The Power of Three)

Sam Hallett had a YouTube channel about conspiracy theories. Kate Wilson, daughter of famous conspiracist George Wilson, became a YouTube star by debunking her father's theories. (AUDIO: The Conspiracy)

Ryan Sinclair had a YouTube channel called RyanS. After his first encounter with the Thirteenth Doctor, and the death of his grandmother, Grace, Ryan uploaded a video entitled "Hey". (TV: The Woman Who Fell to Earth)

Matt Hansen often searched YouTube for old episodes of Doctor X. (PROSE: In Search of Doctor X)

Behind the scenes
In the real world, the Twelfth Doctor title sequence was created by a fan of the show, Billy Hanshaw. Steven Moffat was impressed with the conceptual opening sequence that was popular on YouTube; liking how original it was, he got in contact with Hanshaw for creating an official title sequence.

The Doctor Who series 9 episodes of Doctor Who Extra were released on the BBC YouTube channel.