Facebook blamed the outage on configuration changes it made to routers that coordinate network traffic between its data centers.
"This disruption to network traffic had a cascading effect on the way our data centers communicate, bringing our services to a halt," Facebook vice president of infrastructure Santosh Janardhan said in a post.
Cyber security expert Brian Krebs described what happened as Facebook taking away "the map telling the world's computers how to find its various online properties."
In addition to the disruption to people, businesses and others that rely on the company's tools, Facebook CEO Mark Zuckerberg took a financial hit.
Fortune's billionaire tracking website late Monday said Zuckerberg's personal fortune plunged by nearly $6 billion from the prior day to land at just under $117 billion.
For Facebook's rivals, it was a good day, however.
The messaging service Telegram went from the 56th most downloaded free app in the US to the fifth, according to specialist firm SensorTower.
The encrypted messaging app Signal tweeted that "millions" of new users had joined, and added that it was "Signal and ready to mignal."
It was not the only Twitter user to crack jokes over the outage, though others complained about being cut off from contacts, their sources of income or business tools.
Some were philosophical, however -- such as Cindy Bennett, a baker in New York City, who told AFP: "I think the world would probably be a better place if everybody didn't know what everybody else was doing every second of every minute of every day."
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)