Shortly after midnight, Swedish time, Facebook, Instagram and Whatsapp began to work again after being down for six hours.
On Tuesday morning, Facebook, which owns all three platforms, came out with a first explanation behind the long stop.
According to the company, the reasons were an attempt to change the configuration in a number of routers that coordinate the traffic between Facebook servers.
But the whole thing would instead lead to the sites ceasing to function completely.
"This disruption of network traffic had a snowball effect on how our data centers communicate, causing our services to stop," writes Santosh Janardhan.
Three billion users
According to SVT's tech correspondent Alexander Norén, there is no indication that Monday's stop was caused by an attack.
- It feels a bit like the human factor has been here.
It was so bad that their own internal computer system also failed, says Alexander Norén in SVT's Morgonstudion.
In total, almost three billion users were affected.
- For some, it may seem like a small thing that social media is down for a while.
But in some parts of the world, Facebook and Whatsapp are important digital infrastructure where you get your main news from and communicate with each other, says Alexander Norén.
No user data should have been compromised
In addition to the fact that users during the interruption could not scroll their feeds or write to their acquaintances, it affected the company that is dependent on sales via the platforms - as well as advertisers who use them to be visible.
"To all the people and companies around the world who depend on us, we apologize for the inconvenience of today's outages on our platforms," writes Santosh Janardhan.
According to Facebook, there are no signs that user information has been leaked as a result of the shutdown.