Online aggression-and especially cyberbullying-are topics which have gained substantial attention from researchers as well as public in the past years. While online aggression denotes any aggressive incidents conducted through information and communication technology, cyberbullying is a specific form of this aggressive behavior characterized by the repetition of intended harm via digital media (see e.g., Menesini & Nocentini, 2009; Smith & Steffgen, 2013). Though the first years of research in this field were dominated by a focus on victimization, there is currently growing attention centered on the experiences of those who witness aggressive incidents online-that is, the bystanders of online aggression. This attention on bystanders is highly warranted since their roles are often pivotal in the whole process. Online aggression often takes place in the virtual presence of bystanders (Jones, Mitchell, & Turner, 2015). Similar to offline aggression and bullying (Cowie & Hutson, 2005; Salmivalli, 2010), the responses and reactions of bystanders can influence the course and consequences of the online incidents (Pfetsch, Steffgen, Gollwitzer, & Ittel, 2011). These responses can take on many forms (Pfetsch, 2016; Shultz, Heilman, & Hart 2014), including, in general, offering support to the victim, reinforcing the aggressive acts, or remaining passive. To understand bystander reactions, prior research focused on several individual characteristics, such as age and gender differences, empathy, coping, self-efficacy, anxiety and loneliness, or prior victimization (e.g., Barlińska,