WhatsApp Messenger is a cross-platform instant messaging application that allows iPhone, BlackBerry, Android, Windows Phone and Nokia smartphone users to exchange text, image, video and audio messages for free. WhatsApp is especially popular with end users who do not have unlimited text messaging. In addition to basic messaging, WhatsApp provides group chat and location sharing options. Technically speaking, WhatsApp uses a customized version of the open standard Extensible Messaging and Presence Protocol (XMPP). WhatsApp Inc. was founded in 2009 by Brian Acton and Jan Koum, both veterans of Yahoo.