Dark social is a term used by marketers and search engine optimization (SEO) specialists to describe website referrals that are difficult to track.
Dark social traffic doesn't seem to have a specific source, which creates a challenge for companies that are trying to monitor website referrals and social media activity. Most often dark traffic is the result of people sharing website links through email, text messages and private chats. Because dark social links don't have tracking code automatically appended to their URLs, it is not possible to know how the website visitor found the content.
The term "dark social" was coined by Alexis C. Madrigal, a senior editor at The Atlantic, in a 2012 article. According to Madrigal, data from the Web analytics firm Chartbeat revealed 56.5% of the Atlantic's social traffic was from dark referrals. When Chartbeat analyzed a broader set of websites, that statistic rose to almost 69%.
While Madrigal originally didn't think mobile apps played a large role in dark social, in a 2014 update on the subject, he explained that Facebook mobile apps, as well as other mobile apps, seem to be behind most of today's dark social traffic. This finding could represent a new problem – social media platforms like Facebook may actually have the most power over social traffic, but mobile apps are making it difficult to monitor and analyze.