AP Photo/Paul Sakuma
To put that into perspective, Messenger was only at 200 million monthly active users in April earlier this year.
"Today more than 500 million people are using Messenger each month and we're more committed than ever to make it the best possible messaging experience," said Facebook's director of product management, Peter Martinazzi, in a press release.
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"Asking everyone in our community to install a new app is a big ask," Zuckerberg said. "I appreciate that that was work and required friction. We wanted to do this because we believe that this is a better experience. Messaging is becoming increasingly important. On mobile, each app can only focus on doing one thing well, we think."
Forcing users to choose between downloading Messenger or not being able to message their friends was a move that worked. Messenger quickly rocketed to the top of the App Store, but the app's review page was quickly filled with one-star reviews from disgruntled users and those worried about the app's privacy.
While Facebook's decision to turn Messenger into a required app annoyed users, that moment has clearly passed, and it just goes to show the Facebook ecosystem makes a lucrative messaging app all on its own.
Messenger's 500 million users means the app is now competing with WhatsApp, which reached 600 million monthly active users in August.