This thesis is positioned in the field of communication design research and seeks to critically examine the practice and potential of identity play by digitally networked publics. It defines identity play as entailing a form of identity design practiced by participating publics themselves. The research contributes an understanding of the role of the designer in the entangled networks of digital public space by treating identity design agencies as co-produced with audiences and materials. The thesis locates identity play as part of a productive tradition of anonymous pseudonymity practices. It challenges design assumptions of anonymity as a contemporary privacy problem and of identity as detached and preexisting. The thesis elucidates an intra-active interpretation of identity design as on-going processes of collectively re-making network apparatuses and identity phenomena, moving beyond the limits of centralising and commercial models. It constructs the designer-researcher's role in making space for identity play through taking on the network.

The Creative Exchange (CX) – a UK Arts & Humanities Research Council Knowledge Exchange Hub – provided the space to collaborate and research with diverse consortia of designer-researcher participants and their networked audiences to explore the possibilities of digital public space. The methodology employed by the thesis is grounded theory research through design underpinned by a "diffractive" research stance, with theory and practice read iteratively through each other. I have collected and critically analysed data using "design conversations" with materials, participants and audiences, through multiple projects and prototypes, bounded by the CX Hub and its activities over five years.

The thesis constructs three prototype design patterns to make space for the identity play of networked publics from my practice as a designer-researcher: Sticking together, Fashioning our own belongings and Taking on the network. Each pattern produces an intersection of practices of identity design, networked public participation and design research. The design pattern of Sticking together offers ways of using assemblage to create anonymity and reputation. It calls for and requires the solidarity of collective assembly and ways to make identity play commonplace. Fashioning our own belongings investigates possessions as embodied networked apparatuses of identity, and audience relations as belonging. This design pattern grasps network function and fosters pseudonymity (dis)ownership. Taking on the network is formulated as a performance of inversion by publics through the resistance of the carnivalesque and the responsibility of infrastructural inversions. Taking on the network provides the overarching framework for the design patterns to take on the functions and models of cloud infrastructures.

These findings demonstrate how identity design by publics requires active forms of network literacy that comprehend the network intra-actively, and that it is possible to take on the network by contesting cloud identity apparatuses and models. The design patterns make space for the identity play that, importantly, enables critical and creative anonymity practices to take place. The research offers identity play as a public critical infrastructure with benefits for the resilience and creativity of networked publics. It lends support to designers to reconfigure their part in identity design.

The original contributions to knowledge are: (1) prototype design patterns for making space for the identity play of networked publics; (2) an articulation of the design space for identity play; (3) a diffractive form of design pattern that entails multiple intersecting practices; and (4) an intra-active interpretation of the discipline of identity design.