WhatsApp Messenger  is a proprietary  cross-platform  instant messaging  client for smartphones . It uses the Internet  to send text messages, images, video, user location and audio media messages [ 8 ] [ 9 ]  to other users using standard cellular  mobile numbers .   As of February 2016, WhatsApp had a user base of up to one billion, [ 10 ]  making it the most globally popular messaging application . [ 11 ]   WhatsApp Inc. , based in Mountain View , California, was acquired by Facebook  Inc. on February 19, 2014, for approximately US$ 19.3 billion. [ 12 ] [ 13 ]       Contents    1  History   1.1  Acquisition by Facebook    2  Platform support  3  WhatsApp Web  4  Technical  5  Security  6  Privacy  7  Criticism of business model  8  Competition and shares  9  See also  10  References  11  External links     History  WhatsApp Inc., was founded in 2009 by Brian Acton  and Jan Koum , both former employees of Yahoo! . After Koum and Acton left Yahoo! in September 2007, the duo travelled...