YouTube CEO Susan Wojcicki Screenshot Via YouTube YouTube still isn't a profitable business for Google, sources tell The Wall Street Journal's Rolfe Winkler.

Thanks to a premium ads push last year called "Google Preferred," the video-streaming site increased its revenue to $4 billion in 2014 from $3 billion in 2013, but it's still only roughly breaking even.

The Journal reports that one of YouTube's main problems is that most users watch its videos when they're linked to from — or embedded in — other sites.

"People close to YouTube say the site still struggles to attract users directly, rather than via links," Winkler writes.

However, a YouTube spokesperson refuted that, telling Business Insider that "the majority of watching actually starts on YouTube, not from links, or embeds on other sites."

Ultimately, Google wants people to come to YouTube's homepage in the same way they would turn on the TV — expecting that they'll find consistently high-quality content on different channels.

That's why the company has poured big bucks into helping its original content creators, like Michelle Phan, Bethany Moto, and Epic Rap Battles of History, build their followings and create better videos. The company also redesigned its homepage and tried to improve its video recommendation to hook users into staying longer.

To help boost revenue, the company also plans to roll out more auto-play videos and a new way to target ads using Google search data, Winkler's sources say.

Google acquired YouTube for $1.65 billion back in 2006; Wojcicki took over as YouTube CEO in February 2014.