WhatsApp passed a significant milestone today: the mobile messaging service owned by Facebook now has 1 billion users. That's good news for Facebook CEO Mark Zuckerberg, who spearheaded the jaw-dropping $19 billion acquisition of WhatsApp two years ago on the promise it could grow to become one of the world's most-used communication platforms. So while WhatsApp doesn't make any money, Facebook can certainly say it's popular — more so even than Facebook Messenger, which just passed 800 million users.

WhatsApp had 450 million monthly active users before Facebook acquired it, and the small team led by co-founder and CEO Jan Koum has doubled the user base thanks in part to its ad-free stance and minimal design. According to regulatory filings, WhatsApp's annual sales before the Facebook acquisition were only $10.8 million, a vast majority of which came from charging some users $0.99 a year to use it. Facebook said last month it would eliminate the fee while WhatsApp would remain an ad-free service. The company plans on monetizing WhatsApp by turning it into a tool businesses can use to communicate with customers.

WhatsApp has more than doubled in size since Facebook bought it

Zuckerberg, in a post on Facebook, reiterated WhatsApp's new focus on making money through business partnerships. "Next, we're going to work to connect more people around the world and make it easier to communicate with businesses," he wrote. "There are only a few services that connect more than a billion people. This milestone is an important step towards connecting the entire world."

One billion people now use WhatsApp. Congrats to Jan, Brian and everyone who helped reach this milestone! WhatsApp's... Posted by Mark Zuckerberg on Monday, February 1, 2016

WhatsApp's announcement happens to coincide with another communication tech milestone. Google today announced Gmail now has more than 1 billion active users, although the metrics for calculating activity on an email service tend to differ from those of a mobile app. For what it's worth, Koum seems happy with the achievement, jokingly noting on Twitter how his company never received proper recognition from Silicon Valley.