The announcement comes about 11 months after Facebook acquired the app for US$16 billion, a move that reflected the importance that Facebook places on mobile users.
The latest WhatsApp milestone is significant because it also highlights the recent rise of messaging apps as a more popular and economical option than SMS text messaging, which has suffered declines of nearly 5 percent in countries such as the U.K. In France operators saw SMS traffic on Jan. 1 decline by 10 to 20 percent compared to last year, while the use of MMS, messaging apps and other data traffic rose, according to local media.
"We're thrilled to share that WhatsApp has more than 700 million monthly active users," CEO and co-founder Jan Koum wrote in a post on Facebook. "Additionally, every day our users now send over 30 billion messages."
Facebook's acquisition of WhatsApp received European regulatory approval in October following a U.S. nod in April. At its close, the deal was worth about $21.8 billion due to Facebook stock gains.
When the acquisition was announced in February 2014, WhatsApp had over 450 million monthly users, 70 percent of which accessed the app on a daily basis.
WhatsApp has been steadily growing by about 25 million users per month. It announced April 22 that it had passed the half-billion mark, with new users in countries such as Brazil, India, Mexico and Russia. In December 2013 it had 400 million users.
WhatsApp's growth pace suggests it will reach 1 billion in about a year from now, in December or January. When the acquisition was announced, Facebook CEO Mark Zuckerberg expressed hopes that WhatsApp would hit that threshold.
Facebook said WhatsApp would operate "independently" inside Facebook. In approving the acquisition, the U.S. Federal Trade Commission had called on both companies to proceed with caution in how they deal with customer data following concerns from privacy groups.