There's been little doubt that WhatsApp is one of the most-used cross-platform messenger apps out there, but the company has been rather coy about revealing specific user numbers. Back in April, the WhatsApp CEO did claim his service had a bigger userbase than Twitter's 200 million users and processed 18 billion messages per day (more than Facebook), but now the company's giving more concrete details. According to The Wall Street Journal, WhatsApp has a userbase of over 250 million active users every month, exceeding the 200 million users that Twitter cited on its seventh birthday. While there's no doubt that WhatsApp is one of the most dominant players in the smartphone messaging space, it's an increasingly crowded one — but there's no doubt that it's keeping up with major players like Facebook and Skype, which is a pretty notable achievement for an app that's only four years old.