Here’s what we’ve learned so far about Facebook’s global outage

• Facebook, Instagram, and WhatsApp all went offline Monday for users globally.
• Even the company’s internal communications tools went offline, slowing its ability to respond.
• Here’s what we know so far about possible causes of the outage.
• See more stories on Insider’s business page.

Facebook and some of its most widely used apps, including Instagram, WhatsApp, and Messenger, experienced a major outage affecting users globally on Monday.

Some of Facebook’s internal communications tools were even knocked offline, adding another obstacle to the company’s efforts to get its services back working.

The outage even hit Facebook employees not directly involved in troubleshooting, leading Instagram chief Adam Mosseri to tweet that “it does feel like a snow day” for workers.

Here’s what we know about the outage so far.

What happened?

Around 11:45 a.m. ET on Monday, users around the world reported issues accessing Facebook apps like Instagram, WhatsApp, Messenger, and Facebook itself, via the outage-tracking website Downdetector.

Facebook employees also have had issues accessing internal tools and even physical areas within the company’s offices.

“Devs can’t access their apps online to push new builds, no documentation, nothing. All Oculus platform services are down. No avatars as well,” a developer whose work includes Facebook platforms told Insider.

Facebook security employees also were slowed from assessing the incident because their digital badges stopped working, keeping them from accessing Facebook’s servers, according to The New York Times.

Other Facebook employees were locked out of IoT-connected conference rooms, NBC News reporter Kevin Collier tweeted.

What might have caused the outage?

While it’s early – and even Facebook is still looking into the issue – Facebook employees and internet experts outside the company have shared some initial theories.

A cyberattack likely wasn’t to blame, two Facebook security team members told The New York Times, because it would have been difficult for a single attack to target the wide range of underlying technologies impacted during the outage.

One possibility is an issue with the Facebook-run servers responsible for telling internet users where to find its content.

CloudFlare CTO John Graham-Cumming tweeted that “Facebook and related properties disappeared from the Internet in a flurry of BGP updates.”

CloudFlare describes BGP, or Border Gateway Protocol, as the “postal service of the Internet… responsible for looking at all of the available paths that data could travel and picking the best route.”

Just before Facebook’s outage, Graham-Cunning said, CloudFlare detected “a large number of BGP changes (mostly route withdrawals)” to Facebook’s autonomous systems – basically, the local post office branches.

Security researcher Brian Krebs also said the likely culprit was a misstep on Facebook’s end that caused its services to drop off the internet’s map.

“The DNS records that tell systems how to find http://Facebook.com or http://Instagram.com got withdrawn this morning from the global routing table,” Krebs tweeted.

“We don’t know why this change was made. It could well have been the result of an internal, system wide change or update that went awry. It’s all speculation at this point why. FB alone is in control over its DNS records,” he added.

What is the company saying?

Facebook: “We’re aware that some people are having trouble accessing our apps and products. We’re working to get things back to normal as quickly as possible, and we apologize for any inconvenience.

Facebook CTO Mike Schroepfer also chimed in, tweeting: “*Sincere* apologies to everyone impacted by outages of Facebook powered services right now. We are experiencing networking issues and teams are working as fast as possible to debug and restore as fast as possible.”

Instagram: “Instagram and friends are having a little bit of a hard time right now, and you may be having issues using them. Bear with us, we’re on it! #instagramdown”

WhatsApp: “We’re aware that some people are experiencing issues with WhatsApp at the moment. We’re working to get things back to normal and will send an update here as soon as possible. Thanks for your patience!”