Normally adding 200 million users in 8 months to a product that already has a billion would reduce the average engagement, but most apps don’t have Facebook Messenger’s network effect. Now with 1.2 billion monthly active users, “we increased engagement massively in terms of number of messages sent per active user. We had double-digit growth percentage-wise” Facebook’s head of Messenger David Marcus tells me.

Despite its bots not living up to the hype, Messenger had another banner year. It grew just a bit slower, since last time it got from 800 million to 1 billion users in just six months. But Marcus says the chat app is transcending being where people “find their Facebook friends they don’t have a phone number for.” For some it’s become “a primary communications channel.”

Now it’s working to become more than just the most popular SMS replacement in the Western world.

One approach is copying what’s working elsewhere. Marcus says the app’s Snapchat Stories clone Messenger Day is off to a good start. “Usage with teens is much higher” than some might have expected, “which is cool” Marcus says. “We’ve built a product that teens use on Messenger!” It’s very distributed. It’s going reasonably well The participation rate is very good compared to our best Stories product” he notes, alluding to Instagram Stories. Messenger Day has a big opportunity since its host app has twice as many people on it as 600 million-user Instagram.

Messenger also launched copied Houseparty’s split-screen group video chat. “Group video calling is becoming a big thing with teens especially with masks and effects because it’s live” Marcus notes.

Now the question is how Messenger can make money via ads, not payments, without interrupting the experience. Marcus says structural changes to the app coming at F8 should provide it with new opportunities in this realm.