"Get WhatsApp Messenger and say goodbye to SMS" reads the description for the mobile application.
With such an introduction, it is little wonder WhatsApp has been blamed for the demise of SMS.
The mobile app has become a global hit with its instant messaging (IM) service enabling users to send unlimited text messages for free across all platforms using a data connection. It usually ranks in the top five applications across all the major app stores.
Unlike BlackBerry Messenger or Apple's FaceTime and iMessage, users can communicate with friends that have different handsets. Besides simple text messages, users can also send pictures, videos, and audio media messages enriched with emoticons to their friends. Founded by two ex-Yahoo employees, Brian Acton and Jan Koum in 2009, the IM service has grown to handle 10 billion messages per day as of August, up from 2 billion in April.
It reached 1 million users by the end of 2009, with an estimated 200 million to 300 million users worldwide at the moment according to analyst estimates, the growth spurred on by word of mouth.
According to Allot Communications, a Web-monitoring company, WhatsApp accounted for 18 per cent of IM bandwidth last year, up from 3 per cent in 2010.
This year, the company attracted an US$8 million (Dh29.4m) investment from the venture capitalist firm Sequoia Capital.
WhatsApp offers a free trial for the first year, but requires a yearly subscription fee of $0.99 after the trial period.
On the iPhone, users pay a sign-up fee and can use the service for free thereafter.