This chapter introduces this book’s central focus: how digital platforms are transforming deliberative democratic practices. In the context of democratic disillusionment and complex policy challenges, public institutions have turned to democratic innovations—particularly deliberative ones—to enhance legitimacy and engagement. Simultaneously, the rise of digital platforms offers new tools for participation, yet raises critical questions about inclusion, deliberative quality, and democratic impact. This chapter reviews key theoretical debates and empirical findings on how digital technologies intersect with deliberative ideals, addressing concerns about representativeness, discourse quality, and scalability. It frames the analysis through the input-throughput-output model of democratic legitimacy and highlights the need to assess not just design or process, but also the outcomes of digital deliberation. This chapter sets the stage for the volume’s comparative and conceptual contributions, offering a roadmap for understanding the promises and limitations of platform-mediated deliberation in contemporary democracies