YouTube started out as an off-beat video sharing site. But at its 20th anniversary, the platform's content has fundamentally altered the way we think, feel and interact with each other.

In 2006, Time Magazine named its annual Person of the Year: you. "Yes you," the magazine read. "You control the Information Age. Welcome to your world." Its cover featured a mirror to reflect reader's image – emblazoned on a computer screen tuned to a site modelled after YouTube. It was just a year after YouTube's launch, but already, it had shifted our understanding of the role we would play in the coming era.

This year marks the 20th anniversary of YouTube. It's gone from a novel tool to an unshakable pillar of technological infrastructure. Some 2.5 billion people log on every month. The company says people who watch YouTube on their TVs consume a billion hours of video a day, to say nothing of time spent on the app and website. But as much as YouTube changed how we use the internet, it's had an equally significant impact on our offline lives.

"Not long ago virtually no one took YouTube that seriously," journalist Mark Bergen writes in his book Like, Comment, Subscribe. "But in so many ways, YouTube had set the stage for modern social media, making decisions throughout its history that shaped how attention, money, ideology, and everything else worked online."

YouTube videos have occupied a massive share of our collective consciousness, dictating what brings us together, what drives us apart, what makes us laugh, cry and cringe. "All the dynamics of social media – of attention, fame, disrupting old school media – have mostly grown because of the financial model YouTube built," Bergen tells the BBC. Human nature itself has shifted in the last 20 years, and as seen in these five videos, YouTube would become a nexus point for the way we see ourselves and each other.

Long before the video stitching on TikTok or remixing on Instagram reels, there was Canon Rock, uploaded just 10 months after YouTube's founding. South Korean musician Jeong-Hyun Lim, known online as funtwo, sits in his bedroom with an electric guitar, his face hidden beneath a baseball cap and pixelated footage. A backing track plays the chords to Johann Pachelbel's Canon in D, and Lim joins in, his guitar work subdued in line with the 300-year-old piece. But Lim's playing grows more intricate until, about 40 seconds in, he launches into a blazing solo, fingers gliding across the fretboard.

The reaction was explosive. As the video racked up hits, around 900 users sent direct video responses to Canon Rock – big numbers at a time when uploading videos meant plugging in a digital camera – and thousands more posted their own covers of the song. In 2007, YouTube user Impeto uploaded a compilation of dozens of Canon Rock videos edited into one continuous track, almost as though the whole internet was playing along together. Deft musicianship wasn't new to the web, but the user participation was.

Canon Rock created a "reciprocity between artists" that opened the door for people to see each other as creative partners, says Brooke Erin Duffy, a professor of communication at Cornell University in the US. By democratising the creative process, YouTube created a melting pot for different communities with different interests and skills to make the internet their own.

YouTube turns 20

For more on the world's biggest video platform, read our story on the YouTube statistics Google doesn't want you to know.

It helped inspire a new era of online collaboration, according to Jean Burgess, a digital media professor at the Queensland University of Technology in Australia. Videos like funtwo's weren't just a performance, Burgess says, they were an invitation, a "showcasing of skill and the setting of standards for other players in the 'game' to attain or beat".

Today's video platforms bombard us with marketing partnerships and endless threads of political discourse. But the musicians behind Canon Rock represented a simpler time, where collaboration was not an economic or ideological proposition, but instead a space where online bedroom dwellers were learning to see each other as members of a global community, a project they were all embarking on together.

Early YouTube audiences will probably be familiar with the saga of Bree, better known by the username lonelygirl15. Her story began as a homeschooled girl posting simple videos about her daily life. But things took a bizarre turn when Bree discovered her family was involved with a strange religious cult. Over the weeks and months, the narrative grew more convoluted; Bree ultimately went on the run, investigating secret codes, eluding religious acolytes and fighting a sinister organisation.

It was all fiction, of course. But lonelygirl15's start was so mundane that many didn't question the story until the drama was too fantastic to ignore. "Bree" had an enigmatic realness – she was........

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