Designing Spatial User Interfaces in Mixed Reality: A Systematic Literature Review

We present a systematic review of spatial user interfaces (SUIs) in mixed reality (MR) environments. SUIs organize interface content and interaction through 3D spatial relationships. However, despite the rapid proliferation of prototypes and system implementations, the existing contributions are largely confined to narrowly scoped application contexts, isolated interface components, or discrete interaction techniques, with limited cross-dimensional synthesis. As a result, we still lack a systematic understanding of how core design dimensions interact and co-evolve within MR environments. This absence of an integrative perspective impedes the identification of recurring design patterns and constrains the field's capacity to surface emerging innovation opportunities. To address this gap, we conducted a systematic review of 108 publications across four key dimensions: Display Representation, Spatial Organization, Generation and Update Strategy, and Interaction Method. We further analyzed intra- and inter-dimensional relationships, synthesizing recurring cross-dimensional patterns and distilling their broader design implications. Building on our findings, we propose a four-part research agenda to advance the development of next-generation SUIs for real-world contexts and complex task environments. Our systematic review and supplemental materials are available at https://spatialuserinterface.github.io/ and https://osf.io/sp84u.