Facebook's video views are exploding

Facebook said its users now watch 4 billion videos on its service every day.

That's a big number by any measurement, but it's particularly noteworthy when you consider that it has jumped from 3 billion a day in January.

The increasing popularity of video on Facebook underscores the growing threat that the company poses to Google-owned YouTube. And it bodes well for Facebook's effort to make money from video ads, which command higher rates than other types of online ads.

Part of Facebook's success in video is due to its auto-play video ads, which begin playing in users' newsfeeds automatically with the sound muted. Facebook counts a video as a "view" if the video is displayed in a user's newsfeed for 3 seconds or more, even if the person doesn't actually click on the video to watch with the sound turned on.

During Wednesday's earnings call, Facebook COO Sheryl Sandberg noted that 75% of the video views are happening on mobile devices.