WhatsApp announced Thursday that it now has more than 400 million people using its mobile messaging application every month. The startup has added 100 million new active users in the past four months, CEO Jan Koum wrote in a blog post.
"WhatsApp has just 50 employees, and most of us are engineers. We've arrived at this point without spending a dollar on targeted ads or big marketing campaigns," Koum touted.
The impressive milestone comes amid an all-out war in mobile messaging where upstarts like WhatsApp are going to head-to-head with social juggernauts like Facebook. With an audience of 400 million people, WhatsApp is now one-third the size of Facebook, which has 1.2 billion users.