Facebook's main app has more than 2.3 billion users. We know this because, each quarter, the company reports its user growth, alongside its business updates.

These metrics are a key signal to investors and others about how the company is doing and how quickly it's growing. But that could soon change.

Facebook announced during its quarterly earnings call that it will begin phasing out these metrics for its main app, instead opting to disclose numbers for its "family" of apps, which includes Facebook, Instagram, Messenger, and WhatsApp.

"Over time, we expect family metrics will play the primary role in how we talk about our company, and we will eventually phase out Facebook-only community metrics," Facebook's CFO Dave Wehner said during the call.

That may seem like a surprising move for a company that has billions of users and loves to report vanity metrics as frequently as possible. But Facebook has a good reason for phasing out these kinds of stats — namely, that its once meteoric growth is slowing down.

Facebook's DAUs on the rise again, they even added 1 million in the US after three straight quarters of no growth $FB pic.twitter.com/l4ZQyBPxMB — Karissa Bell (@karissabe) January 30, 2019

To be clear, Facebook is still adding new users, but it's doing so at a slower rate than in years past. That's to be expected from a service with over 2 billion users. The pool of available users remaining is only so big, barring the company's ability to enter China or other currently untapped markets.

At the same time, Instagram and WhatsApp are still growing quickly and becoming increasingly important to the company. Both services also have over a billion users who are highly engaged (in fact, Facebook just revealed that Instagram Stories usage has jumped to 500 million daily users).

As Facebook shifts its focus away from clickbait to emphasize "meaningful" interactions and fights a seemingly never-ending cycle of bad press, it's less clear what engagement with the main Facebook app looks like.

When pressed by investors as to whether Facebook's "rough press cycle" has affected user growth or engagement, CFO Dave Wehner simply said, "I'd probably just let the [daily active users] numbers stand for themselves."

Whether positive or not, it's yet another sign that Facebook is blurring the lines between its services.