This study explores how UK young adults’ exposure to social networking sites (SNSs) and attention to specific SNS content relate to their political practices. Data were collected from a diverse group of undergraduates during the 2015 General Election and Labour leadership campaign via a web survey designed with novel instruments (e.g., simulated Facebook and Twitter newsfeeds). Results indicate that regular use of varying SNSs and attention to certain political content—for example, newsfeeds about student-fee activism—have a positive weak association with off-line formal and activist participation and a considerably stronger association with online "slacktivism." Moreover, exposure to SNSs was found similarly high across respondents. However, those with typical demographic and psychographic markers of participation (e.g., upper socioeconomic status, early political socialization) showed significantly greater levels of engagement with political content and off-line and online participation. Together, these findings suggest that frequent social media consumption is linked to a minimal and narrow mobilizing impact.