Source: comScore [download page]
Notes: Twitter and Instagram are closely matched in total reach, a finding that makes sense given a recent report from the Pew Research Center indicating that a majority of Twitter users also use Instagram. Facebook, of course, continues to stand head-and-shoulders above the rest. Meanwhile, only LinkedIn and Vine are accessed by primarily by desktop-only visitors.
About the Data: All figures are for December 2013.
Related: Social Media Consumption Figures for Key Platforms, on Computers and Smartphones