Check out our playlist of all the YouTube stars who are changing the world:
Celebrity
Justin Bieber looks into the camera, raises his eyebrows and says, "I was found on YouTube." He narrows his eyes. "I think I was detrimental to my own career." This footage, of the teen star's statement in an assault case filed against him by a paparazzo, was uploaded to YouTube by fans in March 2014.
Although his lawyer corrected Bieber's "detrimental" for "instrumental", the slip was fitting: Bieber, once the prodigal Canadian talent discovered on YouTube aged 12, had become gossip column fodder.
Back in 2010, three years after his mother posted a video of him performing in a local talent contest, the doe-eyed, floppy-haired Bieber sold out New York's Madison Square Garden in 22 minutes.
Innumerable artists have since followed Bieber's lead, using YouTube to share their work directly with an online audience, leaving talent agents and other traditional gatekeepers to fame scrambling to catch up. The once-mighty film studios and A&R men have had to get used to a celebrity landscape in which they are no longer the all-powerful star makers.
By nurturing a devoted audience on YouTube - the so-called Beliebers - Bieber also paved the way for a new breed of celebrity: the intensely accessible and "normal" person who can earn a six-figure salary by sharing their thoughts and hobbies online.
Zoe Sugg, better known as Zoella, launched her YouTube channel in 2009. She was a "haul girl", a genre of YouTubers that unveil their new clothing and beauty buys from their bedrooms, like a best friend. Now 24, Sugg has more than 7.6 million subscribers across two YouTube channels. They helped make her 2014 novel, Girl Online, the highest-selling for a debut author since records began.
The first YouTube celebrities emerged from viral one-hit-wonder videos: like Charlie Davies-Carr, the baby who famously bit his brother's finger in 2007 and earned his parents hundreds of thousands of dollars from advertising revenue and merchandise in the process. Tabatha Bundesen gave up her day job to manage her pet, Grumpy Cat. The animal earned more than Gwyneth Paltrow last year.
There are YouTube celebrities in all manner of niche fields. DC Toys Collector is an anonymous "unboxer"; she unwraps new toys. Her video of five Angry Birds eggs being opened has been viewed 90 million times. Tanya Burr has earned 2.7 million subscribers by giving makeup tips. Nearly half a million people have watched Abby Vapes showing how to smoke an e-cigarette like a dragon. Others, such as the blue-eyed Brit Marcus Butler, (3.3 million subscribers), and American LGBT advocate, Tyler Oakley (6.2 million), are famous just for talking.
Beneath the often goofy personas - 23-year-old Butler's most popular video involves him and Oakley sucking on helium balloons - lies steely business sense and an indomitable work ethic.
"YouTubers are the most diligent, hardworking people you could meet, who have doggedly pursued a creative outlet that has turned into a huge media concern over many, many years," explains Dom Smales, founder of Gleam Talent agency, which looks after Suggs, Butler and other social media stars.
While the music industry used to be sniffy about YouTube talent, record labels now fight over musicians who can effortlessly shift records to their online fanbases. "They've done the work, they have the fans and they're super powerful," explains Meridith Valiando Rojas, co-owner of DigiTours Media. "If you have the audience, you have all the leverage."
Bieber's manager, Allison Kaye, says his fans "feel a certain ownership of him, because they feel like they found him even before Scooter [Braun, his agent] found him." But, just as YouTube launched Bieber, it was ready and willing to bring about his downfall. TMZ, the Hollywood gossip site, has released videos of nearly all of Bieber's misdemeanours on its YouTube channel: him urinating in a restaurant kitchen, getting arrested, even footage from inside his prison cell.
The 24/7 scrutiny of modern celebrities has been driven, in large part, by YouTube, where anybody with a smartphone can upload footage of the famous. The competition for exclusive imagery among paparazzi has consequently become savage. In 2013, a photographer was fatally run over trying to get a shot of Bieber after his Ferrari was pulled over by police.
YouTube may have increased the range and pace of celebrity careers, but it suggests that the public's relationship with the famous has stayed the same: we build people only to tear them down again.
And the lure of the new is as intoxicating as ever. Some believe the stars of Vine, an app that allows users to upload six-second videos, are leaving YouTubers in the dust.
Andrew Bachelor, known to his 10.2 million Vine followers as King Bach, is a New York Film Academy drop-out. His slapstick videos have landed him a role on MTV 2's improvised comedy show Wild n' Out. Meanwhile, Jack & Jack, two 18-year-old rappers from Nebraska without a record deal, routinely dominate the iTunes download charts, thanks to their five million followers on Vine.
Shane Dawson, a veteran YouTube comedian with six million subscribers and a burgeoning music and film career, complained to The New Yorker recently: "Vine makes me kind of sad - I'm nervous that will turn into what content is."
YouTube may have transformed what it means to be a celebrity, but the next big thing is surely just around the corner.
- Alice Vincent
Video games
Ten years ago, few predicted that gamers would be the most-followed people on the fledgling video site. But YouTube's most popular channel of all is that of PewDiePie - aka Felix Kjellberg - a 25-year-old Swede who offers profane, hyperactive commentary while playing horror and comedy games. PewDiePie's channel has 33 million subscribers and counting.
To put that in context: if you combined Rihanna and One Direction's subscribers - the two most popular music acts on the website - you would still be four million teeny-boppers short of PewDiePie's "Bro Army".
The concept - watching other people playing video games - has many baffled. But, as Mark Turpin, the CEO of the Yogscast (21 million subscribers) points out, "video is the best way to find out about a video game - to watch it being played. The layer on top of that is the personalities - entertainers - people want to spend time with."
When the Yogscast's founders, Lewis Brindley and Simon Lane, started making video guides to the World of Warcraft game in 2008, cultivating a multimillion-dollar media empire collecting more than 120 million views a month wasn't part of the plan.
But YouTube's gamers engage their audience as if they were friends. And their audience love them for it, regardless of what Variety, the entertainment industry magazine, may think. (It called PewDiePie "aggressively stupid".)
The rise of video streaming on YouTube has led to a major re-think in new game consoles. Both Sony's PlayStation 4 and Microsoft's Xbox One now offer the ability to share gameplay online.
The industry is becoming more savvy about using YouTube to its advantage. PlayStation Access, for example, is a YouTube channel offering videos such as "six multiplayer games that will tear your friendship apart", largely free of the corporate stuffiness you might expect from an "official" source. They're a clear attempt at capturing the spirit of gamer channels.
Getting featured on a prominent YouTube channel can catapult obscure games to mainstream success. In 2012 the British independent developer Mike Bithell released Thomas Was Alone, a minimalist puzzle-platform game that saw reasonable sales. Then it was featured by YouTube channels NerdCubed and TotalBiscuit. "In one week it had doubled the amount of money the game had made," says Bithell, taking it "from a hobby to quit-the-day-job type stuff".
When Bithell moved on to his new project, Volume, did he think about making the game "YouTube-friendly"? "Yeah, I think it would be pretty foolish to make a game nowadays without at least considering it," says Bithell.
Arguably because of PewDiePie's influence, there has been a small boom in independently developed comedy games - see Goat Simulator - while the industry looks to be embracing horror again. Creative Assembly's Alien: Isolation is a first-person chiller with a distinct lack of guns. Publisher Sega will have been well aware of the genre's rise on YouTube.
- Tom Hoggins
Learning
"If this does not blow your mind, then you have no emotion," says Salman Khan. It's a suitably provocative come-on from a YouTube superstar. But he's talking about a maths equation.
Khan is on a mission to bring a world-class, customised education to anyone, anywhere, for free. To do that, he has spent a good part of the last decade in the closet - literally - making around 5000 videos about maths and science.
A decade ago, he was a young hedgefund analyst with a 12-year-old cousin who had fallen behind in maths. He was in Boston, she was in New Orleans, so he began tutoring her remotely, using Yahoo!'s Doodle notepad.
Soon, he started making videos. In them, Khan talks through a concept - perhaps fractions or long division - with the aid of bright numbers on a black screen. His voice is earnest yet informal, the videos are spare and efficient; none is longer than 10 minutes. They feel exactly like getting a private lesson from a whizz of an older brother.
His cousin loved them. "When you're trying to get your brain around a new concept, the very last thing you need is another human being saying: 'Do you understand this?'" he says. On video, his cousin could pause the lesson, or re-watch the parts she didn't understand.
In 2006, a friend convinced him to post his videos on YouTube. Within weeks, strangers were watching the videos, too. "I was getting letters from people all over the planet, saying how my videos had changed their life," he says.
Five years later, he quit his job to work full-time on Khan Academy, the non-profit organisation he founded off the back of his YouTube success. The 75-strong team is now based in California. The lesson style hasn't changed much, but Khan Academy now includes videos by experts in the humanities, too.
Today, Khan Academy has 15 million registered students in 190 countries. The YouTube channel has racked up over 500 million views. Khan's vision for the future has been endorsed by everyone from Bill Gates to Barack Obama; he's working with institutions like Stanford University and the Tate in Britain.
While Khan is perhaps YouTube's biggest success in the field of learning, the platform is saturated with instructional videos. There are YouTube tutorials for changing a light bulb, assembling baby buggies, learning the guitar. Shawn Mendes, the 16-year-old Canadian singer hailed as the "next Justin Bieber", taught himself guitar entirely via YouTube.
Watching a video isn't just quicker than decoding a manual - according to Khan, it's making us smarter. He argues that, by giving us a basic level of knowledge, they help us get more out of experts.
For example, he says: "In the old days, your doctor had to give you all your information. Nowadays, if you think you have something, you spend an hour on some combination of YouTube and Google, and you become pretty smart on the material, so when you go to your doctors, it's you saying, 'Look, I saw this one video, and it mentioned the role of this hormone - is that true? Or can you tell me more about it?'"
Increasingly, traditional educational establishments are embracing YouTube, too. Universities around the world are experimenting with video-based learning via massive open online courses, or Moocs. While there has been some debate over whether the availability of lectures online devalues universities, almost everyone agrees that video tutorials have a role to play in teaching.
Driving the lecture out of the classroom - as Khan would like - is hardly a move towards hypermodernity, he argues. Rather, it takes us back to the Socratic method of tutorials, prizing critical thinking over rote learning.
Who would have thought it? YouTube promoting the classical education.
- Sally Peck
Advertising
The internet was meant to kill off advertising. Instead of sitting through annoying commercials during television broadcasts, we'd go online to watch uninterrupted dramas, comedies and silly clips. Curiously, though, last year's 10 most-watched (non-music) videos on YouTube included four adverts.
We appear to actively seek out adverts on YouTube, be it the titillating 50 Shades of Grey trailer (48 million views and counting), the moving #LikeAGirl campaign (56 million) or, occasionally, the homemade so-bad-they're-good ones.
"In the old days, you would put something on TV and pretty much force people to watch it," says George Prest, executive creative director at the ad agency R/GA London. "These days you have to pull people towards it, which they will only do if they find it engaging."
Bizarrely, considering our supposed shortening attention spans, adverts on YouTube are longer - the 30-second TV spot has morphed into a three-minute online film, with some brands hosting lavish events to celebrate its unveiling. The TV ad has, in effect, become a trailer for the longer, online version. In some instances brands, such as Evian, make adverts exclusively for the internet.
The so-called millennial generation watches far less television than their parents, in large part thanks to platforms like YouTube. And that makes YouTube critical for reaching them.
"Three or four years ago, humour was the category that was most prevalent in branded content," says Scott Button, chief executive of video ad tech company Unruly. "But it's the hardest to succeed with, especially with a global brand, because responses to humour vary so much. If you look at content today, you'll see a lot more warmth, happiness, inspiration, exhilaration."
Some brands have more or less abandoned traditional adverts in favour of partnering with video bloggers on YouTube. These teenagers and 20-somethings uploading homemade videos offer advertisers guaranteed audiences that dwarf what they'd reach on their own. For example, major beauty brands have achieved a collective 511 million video views - a fraction of the 14.9 billion racked up by beauty vloggers.
No wonder British clothing chain TopShop partnered with Zoella (seven million subscribers) last year. When she suggested her viewers click on the TopShop ad in her video for a chance to win a gift voucher, 40 per cent of her viewers clicked. The click-through rate on a traditional banner advert is about 0.1 per cent.
But traditional adverts can still do well. One of the most viewed adverts of all time on YouTube is Evian's "Rollerbabies" - racking up over 100 million views in a year. It is part of a long-running campaign by the bottled water company that started in the late 1990s, before YouTube even existed.
The baby campaign ticks some key online boxes - it is funny, it is cute and it is global (no one ever speaks, babies just gurgle or dance).
Says Prest: "YouTube has forced people to be more entertaining and to listen to customers more." Rather than kill off the ad industry, it has given it an injection of new life.
- Harry Wallop
