Facebook's chat app Facebook Messenger is extremely popular with 800 million monthly active users throughout the world.

Facebook Messenger continues to grow and near the end of 2015, Facebook said it has 800 million monthly active users (MAU), CNet reports.

With the increase to 800 million monthly active users, Facebook Messenger added 100 million new users since it last reported numbers in June.

In the U.S., Facebook Messenger was the fastest growing app in 2015. Messenger had an increase of 31 percent in users year over year, according to Nielsen ratings.

"We are growing very, very fast, and it's all shaping up into thinking about what we can make this year better than last year," said Stan Chudnovsky, head of product for Facebook's messaging efforts.

Facebook also owns WhatsApp, another extremely chat app used around the globe. WhatsApp is preferred by Latin American users, according to monthly active user research done by the app tracking website App Annie.

There are 1.55 billion Facebook users globally and Facebook is trying to make Messenger valuable to everyone. Messenger now allows animated GIFs, payments through the mobile payment company Square and more.

Facebook plans to keep improving Messenger with its own digital assistant called M Concierge and by offering rides from the car-hailing service Uber.

Messenger also allows users to make audio and video calls to their friends all over the world, without charges. The calling feature of Messenger allows the app to compete with Microsoft's video chat app Skype.

Facebook Messenger was included within the Facebook app in 2008. In 2014, Facebook required users to download the separate Messenger app to allow chatting among Facebook friends.

"We believe we have so much more opportunity ahead of us," said David Marcus, Facebook's vice president of messaging products, in a statement. "These are the early days of Messenger." 

With over half of Facebook users on Messenger, the app is definitely a focus for Facebook in the future.