The brainchild of former Yahoo employees and rejected Facebook applicants now has over 900 million monthly users.

WhatsApp, with its short history, has exploded into a global messaging platform since it was founded back in 2009. The app allows users to send text and voice messages without getting charged by mobile carriers. WhatsApp CEO Jan Koum announced that the messaging app has broken the 900 million active monthly user barrier.

The messaging app's popularity gained more traction when it was acquired, ironically, by Facebook. The 2014 deal, for $19 billion, was one of the biggest as far as Silicon Valley deals go. Facebook also spent a couple of billion in its acquisition of Oculus, a popular brand that is currently developing virtual reality head mounts.

Facebook itself has more than 1.4 billion active users per month. However, only half of this number are actively using the integrated messaging system that the social network offers. In short, WhatsApp has surpassed its parent company in terms of active messenger platform users. To further elaborate on how big a milestone WhatsApp achieved, it now has nearly three times the number of active monthly users of Twitter, which stands at 315 million.

Back in August of 2014, WhatsApp reported that it had 600 million active users per month. Another update was released last January 2015 when the app reached the 700 million milestone. The same was done in April of the same year upon reaching 800 million. In just over a year after the acquisition, the user pool had a growth rate of more than fifty percent.

Facebook CEO, Mark Zuckerberg, publicly congratulated Koum on the WhatsApp's success.

"Congrats to Jan, the WhatsApp team and whole community on reaching 900 million people,"  Zuckerberg posted in his personal Facebook page. 

Obviously, next in line for WhatsApp is the 1 billion milestone. The company is expected to make a grander announcement when it finally hits the billion mark.