A few social media platforms have come to play a central role in civil society organizing, often functioning as organizing partners. But on whose terms? As organizing partners, commercial social media platforms shape the conditions under which civil society actors organize, also shaping organizational dynamics, visibility, and collective action. Far from being neutral partners, these platforms become battlegrounds where civil society actors and platform owners negotiate power, visibility, and control?differently affecting various forms of civil society actors and organizing. Therefore, we need to move beyond the notion of platforms as mere organizing agents to critically examine the opportunities and constraints they create for different civil society actors, as well as how different civil society actors navigate these. This requires considering both exogenous, contextual elements, and endogenous, actor-centered elements of civil society organizing. Doing so allows us to examine how organizing efforts emerge not simply on social media platforms but with them, requiring constant negotiation with platform logics. The collection of articles in this special issue shows how social media platforms enable civil society organizing, but also how platform-driven asymmetries emerge and play out differently according to the different features that characterize the civil society organizations at stake.