As you’ve all but certainly heard, Facebook had a major outage midday on Friday. Overall traffic on news sites dropped by 3%, thousands took to Twitter to voice their frustration, and, apparently, a select few called the LA Sheriff’s Department. Most interestingly for us, the Facebook outage provided a natural experiment to look at what the world of web traffic looks like without Facebook. Here, I’ll delve into two issues that are particularly interesting to look at through the lens of the outage.

Facebook and dark social

So-called “dark social” traffic — traffic to articles that lacks a referrer because it comes via HTTPS or apps — is subject to endless speculation. What portion of it comes from emailed links? From links sent via instant messaging? From standard social sources like Facebook and Twitter but with the referrer obscured? From search sites that use HTTPS? By virtue of the fact that no explicit referrer is sent, it’s impossible to tell for sure. Since Facebook makes up a huge portion of non-dark traffic, one might guess that a big chunk of dark traffic is actually Facebook traffic in disguise.

Of course, during the outage virtually all Facebook traffic was stopped, so we can use that data to ask how much dark traffic was definitely not coming from Facebook. The answer? Very little of it was coming from Facebook directly. Take a look at the graph below.

Facebook referrals dropped by almost 70% during the outage (note that traffic didn’t drop to 0, presumably because some number of people had Facebook pages open before the outage). There’s certainly a drop in dark social, but it’s not nearly as stark, and dark social traffic just before the outage was only 11% higher than at its low point during the outage. Since 70% of Facebook traffic dropped off, that would imply that at most 16% (11% / 70%) of traffic could’ve been directly attributable to Facebook.

Now, of course, we’d expect some other social sharing might be negatively impacted — if people aren’t discovering articles on Facebook, they might not be sharing them in other ways. So, that doesn’t mean that 16% of dark social traffic is from Facebook, but it does provide strong evidence that 84% of dark social traffic is something other than Facebook traffic in disguise.

Where people go in an outage

As I discussed in my last post, a huge percentage of mobile traffic comes from Facebook. Given that, we’d probably expect mobile traffic to be hardest hit during the outage. And, indeed, entrances to sites on mobile devices were down 8.5%, when comparing the minute before the outage to the lowest point while Facebook was down.

Interestingly, though, we see the opposite effect on desktops: a 3.5% overall increase in desktop traffic after the beginning of the outage. That increase was largely fueled by a 9% increase in homepage direct traffic on sites with loyal homepage followings. We saw no increases in traffic via other referrers, including Twitter and Google News, during the outage. While we certainly can’t claim that the outage was the cause of that uptick in desktop traffic, the timing is certainly notable.

In short, then: our brief world without Facebook looked a bit different, albeit in predictable ways. Significantly less news was consumed on phones, slightly more homepages were visited on desktops, and 30 minutes later, when Facebook came back online, traffic returned to normal.