WhatsApp has finally launched video calling across its entire platform - meaning that iPhone, Android and Windows Phone users can use the feature together.

The feature has been teased for months, but the messaging app (that boasts over a billion users) announced it in a blog post today.

It puts the Facebook-owned app in direct competition with the likes of Apple's FaceTime, Microsoft's Skype and Google's recently-released Duo app .

"We’re introducing this feature because we know that sometimes voice and text just aren’t enough. There’s no substitute for watching your grandchild take her first steps, or seeing your daughter’s face while she’s studying abroad," WhatsApp said.

"And we want to make these features available to everyone, not just those who can afford the most expensive new phones or live in countries with the best cellular networks."

Because WhatsApp uses data, rather than a phone signal, it can be used over Wi-Fi, which makes it a popular choice for people who want to keep their bills down.

All you need to do to access a video call is hit the call button in the top right hand corner and choose whether you want to make a voice or video call to your contact. It's possible to switch the camera mid-call from the front-facing to the rear camera on your phone.

"Over the years we’ve received many requests from our users for video calling, and we’re excited to finally offer this feature to the world," the company said.

This is the latest in a series of new features from Facebook-owned WhatsApp. Recently it has added the ability to tag users in group chats and add stickers to messages just like Snapchat .

It also decided to share all of your user data with Facebook, in a move that got some people a little bit angry . However, pending an investigation from the European Union, the two companies have paused their sharing agreement.