Facebook has suffered the most severe outage in its history, with key services rendered unusable for users globally for much of today.
The last time Facebook had a disruption of this magnitude was in 2008, when the site had 150 million users - compared with around 2.3 billion monthly users today.
Facebook's main product, its two messaging apps and image-sharing site Instagram were all affected.
Facebook's apps seemed to be recovering by this evening, with Instagram announcing it was back.
We’re aware of an issue impacting people's access to Instagram right now. We know this is frustrating, and our team is hard at work to resolve this ASAP.— Instagram (@instagram) March 13, 2019
The cause of the interruption has not yet been made public. Facebook, which gets a vast majority of its revenue from advertising, told Bloomberg that it was still investigating the overall impact "including the possibility of refunds for advertisers".
"We're aware that some people are currently having trouble accessing the Facebook family of apps," Facebook said in a statement.
"We're working to resolve the issue as soon as possible."
In response to rumours posted on other social networks, the company said the outages were not a result of a Distributed Denial of Service attack, known as DDoS - a type of cyber-attack that involves flooding a target service with extremely high volumes of traffic.
An NBC News broadcaster reported the cause was related to "overloaded" databases.
Widespread disruption hits businesses
Estimates suggest the issue began around 3am New Zealand time. While Facebook's main service appeared to load, users reported not being able to post.
Those on Instagram were not able to refresh feeds or post new material. Facebook Messenger's desktop version did not load - but the mobile app appeared to allow the sending of some messages; however, users reported glitches with other kinds of content, such as images. WhatsApp, Facebook's other messaging app, had similar problems.
A third-party outage map suggested the problem was global - DownDetector monitors posts on other social networks for users mentioned a loss of service elsewhere.
The issue also affected Facebook Workplace, the companies service for businesses to communicate internally.
Buenos Aires-based designer Rebecca Brooker told the BBC the interruption was having a significant impact on their work.
"Facebook for personal use is fine - but what happens when we rely on large companies such as this to provide business services?" she said.
"I'm trying to communicate with my team in New York. Facebook Workplace is our only channel for [communication] with the exception of email."
Facebook users, including brand marketers, expressed their outrage on Twitter with the #facebookdown hashtag.
"Ya'll, I haven't gotten my daily dosage of dank memes and I think that's why I'm cranky. A #FacebookDown," user Mayra Mesina tweeted.
The outage is occurring against a political backdrop of legislators in the United States and beyond considering whether large technology firms - not just Facebook - should be broken up.
Elizabeth Warren, who is hoping to be the Democratic candidate in the next US presidential election, told the New York Times: "We need to stop this generation of big tech companies from throwing around their political power to shape the rules in their favour and throwing around their economic power to snuff out or buy up every potential competitor."
On the latest issue, Ms Brooker added on Twitter: "Look at what happens when we let one company control everything.
"I figured this could happen eventually but it's extremely crippling to be part of this monopoly."
Reaction ranges from panic to humour
While Facebook and Instagram have been down, many have turned to Twitter to make jokes about the outage.
The hashtags #FacebookDown and #InstagramDown have been used more than 150,000 times so far.
Some Twitter users who work in "Facebook-centric" jobs, expressed their panic and distress at being unable to use the platform.
Many shared jokes about the social media outage leading to the collapse of society, as "nobody remembers how to reach loved ones or eat food without posting updates".
The date is March 14th 2019. 24hrs after #facebookdown— Elevator Thoughts (@Jonny_LDN) March 13, 2019
Nobody remembers how to reach loved ones or eat food without posting updates and the global economy has collapsed.
The few Facebook users that migrated to twitter were among the lucky few to once again connect. pic.twitter.com/Q8OvfWc2uk
Some users reflected on how the outage had exposed their reliance on the social media networks, while some joked that the lack of access to Facebook would deprive them of validation.
- BBC /Reuters