One billion people now use WhatsApp each month.
After seven years, the messaging service now sees 42 billion messages, 1.6 billion photos, and 250 million videos sent daily.
"We are proud of this milestone, and we're humbled by the extraordinary ways all of you have used WhatsApp," the company said in a blog post.
The app, now available in 53 languages, has been used to share information during natural disasters and health emergencies, find a date, grow small businesses, and just keep up with far-flung family and friends.
In September, CEO Jan Koum announced that the service had reached 900 million monthly active users. Five months later, it had racked up another 100 million.
"But now, it's back to work—because we still have another 6 billion people to get on WhatsApp, and a long way left to go," the company said.
When Facebook acquired WhatsApp in 2014, CEO Mark Zuckerberg said the app was appealing because it was "on its way to 1 billion users, and any Internet service that tops that milestone is extremely valuable."
Facebook hit the 1 billion mark in the fall of 2012. In August, it announced another first: one billion people used Facebook in a single day.
This WhatsApp milestone, meanwhile, comes just after it ditched its annual fee. After one year of free texting, folks were automatically charged 99 cents—a small price to pay for instant communication. But many WhatsApp users don't have a debit or credit card number, and worried they'd lose access to friends and family, the company said recently.
"So over the next several weeks, we'll remove fees from the different versions of our app and WhatsApp will no longer charge you for our service," according to an announcement.
Gmail, meanwhile, also topped 1 billion monthly active users, Google CEO Sundar Pichai announced on a recent earnings call, The Verge reports. The 11-year-old email service reached 900 million in May.