By William Oyo-Ita 2 February 2016
A message on the app's blog section said: "One billion people are using WhatsApp. That's nearly one in seven people on Earth.
"We are proud of this milestone, and we're humbled by the extraordinary ways all of you have used WhatsApp.
"WhatsApp began as a simple idea: ensuring that anyone could stay in touch with family and friends anywhere on the planet, without costs or gimmicks standing in the way.
"So even as we celebrate this achievement, our focus remains the same.
The California-based firm announced the milestone just six years after it was founded by ex-Yahoo! employees Brian Acton and Jan Koum.
The app's popularity has stemmed from its allowing groups of people to stay in touch simultaneously without having to enter contact details.
As well as text messages, users can also share photos, videos and other media.
It also offers a similar secure messaging service to the BlackBerry and has become more popular as the Canadian phone maker has seen its handsets fall in popularity compared to those made by other smart phone makers.
