This dissertation focuses on ‘civic tech’, the global phenomenon of tech-based voluntary action of citizens emerging with the rise of the culture of openness and sharing and initiatives of open government data. What does the ‘civic’ of civic tech mean? And what makes civic tech democratic and democratizing? These questions have been rarely asked or conveniently understood with Western-based theories and cases of tech-oriented civic actions. Combining critical studies of technology and civic engagement with the emerging scholarship of digital citizenship, I use the concept of digital citizenship as a heuristic tool to examine how digital and data technologies intervene in the way we form our civic identities and act as citizens. Based on 15-months of ethnographic fieldwork (2017-19) with civic tech groups for civic hacking, data activism, and platform cooperativism in Seoul, South Korea, I provide empirical analysis on how civic hackers articulate their digital citizenship as a new form of civic identity overcoming the developmental nationalism. I also provide contextual explanations how the democratic potential of civic tech unfolds in civic hackers’ lifeworld through their everyday practices of civic tech confronting injustices and inequalities in Korea. I argue that grassroots civic hackers’ struggles to reconfigure the global hegemonic discourses of civic tech provide alternative epistemologies and practices to enable more equitable and decentralized democratic systems, which is increasingly important in the contemporary crisis of democracy and ongoing datafication in the world.