For the last three years, YouTube has put on a series of increasingly extravagant parties meant to convince advertisers that the video platform is the best place to spend their marketing dollars. The fourth annual Brandcast took place last night at the Javits Center, and compared with previous versions, it was decidedly more self-assured. In the past, YouTube spent a lot of time assuring the brands in attendance that its content was safe, high-quality, and watched by more than just bored teenagers. This time YouTube CEO Susan Wojcicki cut to the chase.

"Today, I’m happy to announce that on mobile alone YouTube now reaches more 18–49-year-olds than any network — broadcast or cable. In fact, we reach more 18–49-year-olds during primetime than the top 10 TV shows combined," she said, citing data from a Nielsen study of US viewers commissioned by Google. "At a time when TV networks are losing audiences, YouTube is growing in every region and across every screen."

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Those numbers are a bit vague. We don't know exactly how many people are watching, or whether any individual channel comes close to matching the reach of network TV programming. Most importantly, that doesn't break out what percentage of the audience is watching Google Preferred content, the pre-approved brand-safe stuff that nets big ad dollars, versus the long tail of cat videos and home movies that have steadily dwindling value. Still, it seemed clear that YouTube's clout was not lost on the agencies handling big budgets. Wojcicki used her time on stage to announce that Interpublic Group, one of the world's largest ad holding companies, planned to shift $250 million from traditional TV networks to YouTube over the next year.

YouTube had lots of its creators on hand to help demonstrate its cultural clout, and the display was impressive. The rapper Silento performed "Watch Me," the track behind the biggest dance craze of the last year. Andra Day told the story of being an unknown musician sharing her songs on YouTube, where she was discovered. And she brought the house down with a performance of her Grammy-nominated track "Rise Up," a track with lyrics that are now plastered across 40 million Coca-Cola cups at McDonalds across the nation.

Unafraid to be weird

The presentation gave heavy emphasis to YouTube as a safe space for the LGBT community. Along with emotional clips of creators coming out to their fans, we saw Ingrid Nilsen interviewing President Obama on the topic of gay marriage. And the presentation didn't shy away from the weird, edgy stuff that gives YouTube its character. While previous Brandcasts featured big names like Jay Z, Pharrell, and Bruno Mars, these were mainstream acts with no particular tie to YouTube. Last night's performance was by Sia, an artist whose rise to prominence was propelled by YouTube as much, if not more, than radio or record sales.

"Just two weekends ago, we partnered with Coachella to deliver the first ever major 360-degree livestream," said Robert Kyncl, YouTube's chief business officer, as he introduced Sia. "During the first weekend, over 21 million people tuned in to watch Coachella on YouTube—almost twice as many as tuned in to watch the season finale of American Idol."

It was quickly clear that very few of the corporate suits standing around me in the crowd had any idea who Sia was. They certainly didn't know her music, save for a rendition of Rihanna's "Diamonds" (which Sia wrote). And the act was dark and strange, with dancers in giant puppet heads attacking one another. But as she ran through a performance she recently premiered at Coachella, the energy onstage captured the crowd. Among all the big speeches and data points dropped during the evening, Sia's performance was the biggest statement of all. YouTube didn't need a name everybody knew. It knows what people like, what they connect with. And it has the views to prove it.

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