Amazon Mechanical Turk (AMT) offers a relatively low-cost alternative to traditional expensive survey samples, which likely explains its popularity among survey researchers. An important question about using such samples is whether they are representative of the larger Internet user population. Though prior research has addressed this question about demographic characteristics, little work has examined how AMT workers compare with others regarding their online activities—namely, social media experiences and online active engagement. This article analyzes survey data administered concurrently on an AMT and a national sample of U.S. adults to show that AMT workers are significantly more likely to use numerous social media, from Twitter to Pinterest and Reddit, as well as have significantly more experiences contributing their own online content, from posting videos to participating in various online forums and signing online petitions. The article discusses the implications of these findings for research that uses AMT as a sampling frame when examining questions related to social media use and active online engagement.