Facebook-owned WhatsApp announced Monday that it now has one billion monthly active users, who send 42 billion messages and share 1.6 billion photos a day. The announcement comes after WhatsApp announced 900 million monthly active users last September, and just days after Facebook CEO Mark Zuckerberg announced 1.59 billion monthly active users for the social network.

Reaching a billion users is a big milestone for WhatsApp, but it’s also a bit of a validation for Zuckerberg. To justify Facebook’s $19 billion acquisition of WhatsApp two years ago, Zuckerberg predicted that the app would eventually reach a billion users. At the time of the acquisition, WhatsApp had 450 million monthly active users.

However, the announcement Monday raised eyebrows for other reasons: WhatsApp announced the new milestone just as Alphabet was conducting its Q4 2015 earnings call, during which Google CEO announced that the company’s Gmail email service now has more than one billion monthly active users.

Google and Facebook compete on multiple fronts with each other, with Google still having the upper hand with many established services, while Facebook has been more aggressive in pursuing newer consumer technologies. As a result, Facebook has a wide lead in messaging, where WhatsApp’s strongest competitor is Facebook’s own messenger.