Since 2021, we’ve been conducting in-depth research into how people respond when they witness hostility online. In this section, we share what we've learned from large-scale surveys, interviews with bystanders, and experiments on a simulated social media platform. Our focus is on understanding why some people step in to help, while others don’t. We explore the different factors that encourage action, like the severity of the hostility, as well as the barriers that hold people back, such as fears of backlash, lack of knowledge, or uncertainty about how to respond.