Facebook announced it's rolling out live video streaming to all iPhone users across the US, in an effort to take on Twitter's Periscope service for users to share moments of their life as they're happening.

The live streaming functionality is built right into the Facebook app available on the iTunes App Store. It was introduced in December 2015 to a small subset of users, but now it's rolling out to the masses. Facebook said live streaming will be available to the rest of the world and Android users over the coming weeks.

To share live video, Facebook said, you simply tap on Update Status and then select the Live Video icon. You can write a quick description and choose the audience that you want to share with before going live. During your broadcast, you'll see the number of live viewers, the names of friends who are tuning in, and a real-time stream of comments to interact with your audience.

When you end your broadcast, the video stream will be saved on your Timeline like any other video, which you can then delete or keep for your friends to watch later. Facebook will enable users to discover live streaming directly from their News Feed, where they will see their friends and public figures in the moment.

So what's the difference between Facebook and Periscope? After you start a stream on Facebook it will only be shared with your friends, whereas Periscope's Twitter integration tweets to the whole world.

Facebook has made a big bet on video. During the company's earnings report on Wednesday, CEO Mark Zuckerburg said there are 500 million people consuming 100 million hours of video per day on Facebook.

"We're also exploring ways to give people a dedicated place on Facebook for when they just want to watch videos," Zuckerberg said.