Governments are in need to innovate public service. They struggle with complex societal problems, decreased citizen trust and the work of adapting to new demands related to how service should be delivered to fit contemporary living. Inspired by success stories from the private sector's "open innovation" approaches, governments are complementing internal competence with knowledge resources of external actors such as citizens. One increasingly growing strategy for knowledge expansion beyond government boundaries has been to use social media platforms, e.g. Facebook, Instagram and Twitter. This strategy has been shown to be especially effective at a local government level (henceforth municipality) where citizens are geographically close to the government and where government manages activities that citizens rely on in their daily lives.

Despite an expansive rise of social media use in municipalities, and efforts to see beyond a traditional and New Public Management approach to public service, there is little knowledge about the participatory and innovative capacity of social media in a government context. This knowledge gap is reflected in researchers' and municipal administrators' uncertainty as to how to make use of social media for improvement of public service and how to handle tensions about what is possible to do with social media and what is legitimate to do as a public servant.

The aim of the thesis is thus to map, unpack and conceptualize social media practice by municipal communicators to understand how tensions and dynamics between social media mechanisms and government rationales are shaping the practice and how new emerging practices can be understood as public service innovation. The research questions of the thesis are: RQ1: How are social mediamechanisms supporting different public service rationales?; RQ2: How is public service enacted in the social media practice by municipal communicators?; RQ 3: How can social media practice by municipal communicators be understood as public service innovation?

With an engaged scholarship research approach, related research on social medialogic, e-government, e-governance and digital public service innovation, and with the help of the theoretical perspectives "service innovation," "practice perspective" and "sociomateriality," the thesis contributes extended insights into how social media platform mechanisms support different government rationales in processes of sociomaterial service, and how such practice can be understood as creative processes towards public service innovation.

As a practical contribution I propose that both communicators and managers in government engage together in networks of others working with social media and to discuss for instance the mission of the government in relation to the aim of using social media, what tensions arise in the social media practice and why, and how algorithms are shaping the social media practice.