When YouTube co-founder Jawed Karim uploaded that first video of Me at the Zoo in 2005 it was hard to imagine what the video sharing site launched under the slogan “broadcast yourself” might become.

These days, A-list celebrities like Will Smith and professional athletes like Golden State Warriors standout Kevin Durant use YouTube to afford intimate if controlled glimpses of their private lives, even as not-ready-for-mainstream players like gamer Mark Fischbach (better known as Markiplier) or beauty guru Michelle Phan rake in millions.

YouTube has fundamentally transformed the media landscape. It democratized video creation and distribution, providing a platform where anyone with a camera, an internet connection and a passion for storytelling can reach a global audience. It gave rise to a whole new creative class of influencers, who were able to bypass the entertainment industry’s gatekeepers and tastemakers.

And its reach is, in a word, enormous. Some 1.5 billion users around the world log in every month, binging on 1 billion hours of video a day. Their viewing choices are virtually endless. 400 hours of video is uploaded every minute, or about 100,000 years’ worth of content.

But its rise as a global video powerhouse has not been without controvery. The site blocked an extremist American cleric’s messages in 2017 following a spate of domestic terror attacks and faced with mounting pressure from governments and counterterrorism advocates to crack down on jihadist propaganda videos. And some of YouTube’s self-made stars, like Felix ‘PewDiePie’ Kjellberg and Logan Paul, have caused outrage with their unfiltered uploads.

In an effort to assuage worried advertisers, YouTube updated its guidelines, tightening its policies about what content can appear on the site and applying stricter criteria to which channels and videos would be eligible for advertising. It also announced it was stepping up enforcement. CEO Susan Wojcicki said YouTube would invest in machine-learning technology to train its algorithms to recognize and take down videos that violate its polices, and hire 10,000 people this year to work alongside the machines, to fine-tune the review process.

YouTube’s more aggressive stance about policing the site has translated to less money for some, provoking protests within the legions of amateur video bloggers and personalities who populate the site. That dismay erupted in a tragic display in early April, when a woman angered by what she viewed as censorship of her workout videos traveled to YouTube’s Northern California headquarters with a gun and injured three people before killing herself.

Robert Kyncl, YouTube’s chief business officer says the last 12 months have forced YouTube to focus on the “four freedoms” that are core to the platform: freedom of expression, freedom of information, freedom of opportunity and freedom to belong. “We know what we mean for the world because of those four freedoms, and we want to makes sure we uphold them—but uphold them responsibly.”

Kyncl says YouTube has been gradually laying the infrastructure to manage the unprecedented scale, like a boomtown racing to prop up its services to care for a rapidly growing population. “What you’ve seen over the last 12 months is, some things were ahead of us. We did not have the infrastructure fully in place yet,” Kyncl says. “I think that today we are better prepared than anyone because we have spent so much time on it and invested so much into it.”