WhatsApp is now home to 400 million monthly active users

WhatsApp now has more than 400 million monthly users, according to a blog post published by the company’s CEO Jan Koum. Even more stunning: Koum says his company added 100 million monthly active users in the last four months.

A few short years ago, my friend Brian and I set out to build a messaging service with a single focus: best possible user experience. We bet that if our team of engineers could make messaging fast, simple, and personal, we could charge people directly for the service without having to rely on annoying banner ads, game promotions, or all those other distracting “features” that come with many messaging apps.