Facebook on Monday began rolling out video calling on its Messenger mobile application, enabling face-to-face conversations among users of the app around the world.
With the new feature, users can add video to calls to another person with the same application.
"You can quickly start a video call from any conversation with just one tap," Facebook said in a statement.
"If you're messaging with someone and realize that words just aren't enough, you can simply choose the video icon in the top right corner of the screen and start a video call right from within an existing Messenger conversation."
Similar services are offered by Microsoft's Skype, Google Hangouts and Apple's FaceTime.
Facebook last year broke off Messenger from the main Facebook application for mobile users, creating a separate platform which now has some 600 million users.
The world's biggest social network also opened up Messenger to outside developers as part of its strategy to create a "family" of apps that also includes Instagram and WhatsApp.
Free calling has been available for two years to users of Messenger, although people may be required to pay for data used during the connections.
"Video calling will expand Messenger's real-time communication features, enabling the more than 600 million people who use Messenger every month to reach others wherever they are, from anywhere," the statement said. "It's fast, reliable and high quality."
Video calling in Messenger is launching for people using Apple or Android devices in Belgium, Britain, Canada, Croatia, Denmark, France, Greece, Ireland, Laos, Lithuania, Mexico, Nigeria, Norway, Oman, Poland, Portugal, the US and Uruguay and will hit more countries over the coming months.
Facebook has offered few hints on how it will monetize Messenger, but recently unveiled a system of peer-to-peer payments which could be adapted as an e-commerce platform.
Another Messenger allowed users to communicate with online merchants, essentially turning formerly impersonal Internet shopping into ongoing text message conversations.