WhatsApp is an instant messaging service based in Santa Clara, Calif., that reached 400 million monthly users.
Facebook just bought the company for $US16 billion.
According to The Telegraph, WhatsApp sends 20 billion messages per day — double the size of Facebook’s daily messaging traffic, carried by Messenger.
The app was created in 2009 by former Yahoo! employees Brian Acton and Jan Koum. WhatsApp allows you to send text messages, audio, and video to others — as long as you subscribe. But as long as you have a strong internet connection, the app will never add additional roaming charges to your phone.