An ad-free instant messaging service for all major smartphones from WhatsApp Inc., wholly owned by Facebook. Founded in 2009 by Brian Acton and Jan Koum, WhatsApp uses the Internet as an alternative to the SMS text messaging system. Via Wi-Fi, subscribers pay nothing for WhatsApp messages the first year and 99 cents per year thereafter. If Wi-Fi is unavailable, and people use their cellular data plans for WhatsApp messages, thousands can be sent for a fraction of total usage because text takes up very few bytes (characters).WhatsApp also provides voice calling from one WhatsApp user to the other, as well as voice recording, which lets users record and send audio messages instead of typing.With more than 400 million monthly users worldwide and billions of messages sent each day, Facebook acquired the company for USD $19 billion in 2014. See SMS and Facebook Messenger.