(CNN) - Mobile users who have gotten used to chatting with their friends via Facebook will soon have to make sure they've downloaded the social-media giant's app designed specifically for that.
Facebook has begun notifying mobile users that they'll no longer be able to text via its core app.
Instead, they'll need to download Messenger, the dedicated texting app Facebook rolled out in 2011.
The company started notifying some users last week.
The update will roll out first to Android and iOS users in a handful of European countries, according to a Facebook spokeswoman.
In November, after Facebook launched Messenger 3.0, the company discontinued messaging in the core Facebook app for people who already had Messenger.
The good news for people still using just the Facebook app is that they'll be able to message friends in much the same way they do now. Once both apps are installed, tapping the "message" icon on the Facebook app will simply send the user to Messenger. They'll be able to return via a "return to Facebook" icon.
Facebook and mobile messaging have been linked in many folks' minds since last month, when the company shelled out a staggering $19 billion for WhatsApp, a texting app far more popular overseas than it is in the United States.
Despite speculation, Facebook said at the time that it has no plans to merge WhatsApp, which lets users send unlimited messages for no more than 99 cents a year, with Messenger.
Both are part of a maturing set of apps that are marginalizing cellular plans that charge for texting. Unlimited texting is already standard with many mobile plans in the U.S., but not so much in places like India, Africa and South America, where WhatsApp is most popular.