WhatsApp claims it has half a billion users
That is up from an estimated 450m it had in late February, as the service's reach expanded rapidly in countries including Brazil, India, Mexico, and Russia.
WhatsApp said on its blog that its users are also sharing more than 700m photos and 100m videos a day.
Facebook founder Mark Zuckerberg announced in February that his social network is buying WhatsApp for US$19bn.
The stock and cash purchase marries WhatsApp's steadily growing user base with Facebook's 1.2bn active users.
The huge price tag raised eyebrows but Zuckerberg told the Mobile World Congress in Spain days after the announcement that he believes WhatsApp is actually worth much more.
He argued that there are very few services that reach so many millions of people in the world.
The acquisition would be Facebook's largest ever.
Source: AFP via I-Net Bridge