The social network giant said it would include the alerts at the top of feeds on Facebook and Instagram, starting in the United States with plans to expand in the future.
"With the rise in Covid-19 cases in the US, we're putting an alert at the top of Facebook and Instagram to remind everyone to wear face coverings," the company said in a statement.
Facebook will also include additional prevention tips and links to public health agencies in its Covid-19 Information Center.
Twitter appeared to join in the call for masks with a sardonic message which referred to a longstanding demand from users for a tweet edit button.
"You can have an edit button when everyone wears a mask," said a tweet from the official Twitter account, which was shared some 93,000 times within an hour.
The moves come amid a rift in some parts of the United States on the need to wear masks, with some Americans rejecting the face coverings as government intrusion.
President Donald Trump, who has yet to be seen in public wearing a face mask during the crisis, said this week he would have "no problem" doing so under certain circumstances.
"If I were in a tight situation with people, I would absolutely," Trump said in an interview with Fox Business, as many US states reported a surge in the number of cases.
Heath experts expressed alarm last month when Trump held a rally in Tulsa, Oklahoma, without requiring attendees to wear masks.
Eight members of his campaign staff working at that event tested positive for the virus.
New Look, Facebook Dating: Big Announcements From F8
The Future Is Private
After a tumultuous 2018, Facebook founder Mark Zuckerberg stressed on a privacy-focused social network at the Facebook F8 developer conference this year. In the keynote, Zuckerberg said that they are pushing hard on helping people to connect with close family and friends. He unveiled a revamped and redesigned version of Facebook, called the FB5 which aims at making navigation easier, improve the loading time and giving the user a cleaner appearance. The updated mobile app is rolling out now. The desktop version will be released in the next few months.
Along with changes to the core app, Facebook also announced updates to Instagram, Facebook Messenger, Oculus Quest and Rift S virtual reality headsets — and introduced a new feature, Facebook Dating.
Here's a look at all things new.