Whatsapp messenger is a proprietary, cross-platform instant messaging application for smartphones. in addition to text messaging, users can send each other images, video, and audio media messages. the client software is available for: android; blackberry os, blackberry 10, ios; series 40, symbian (s60); and, windows phone. the company by the same name was founded in 2009 by brian acton and jan koum, both veterans of yahoo! and is based in santa clara, california.