The present study investigates the standardization process of contact tracing apps during the COVID-19 pandemic. Due to the epidemiological urgency, and differing from classical examples in the literature, this process is characterized by a compressed timeframe. In this setting, we investigate the role of different standard-setting modes and their interaction through the lens of multi-mode standardization. We find that the processes of standard setting through market competition or inclusive multi-stakeholder committees proved time-consuming and inefficient in addressing the immediate needs during this major global health crisis. Multi-mode standardization between committees, market players, and governments equally proved unable to coordinate a standard. Ultimately, a so far neglected actor, namely platform owners, proved to be pivotal in coordinating a widely-adopted standard. Our research extends multi-mode standardization with platform owners as a further standardization actor of proliferating importance given the increasing pervasiveness of platforms in numerous contexts. The present article provides implications for the interplay between different modes of standard setting in general, and the setting of technological standards in crises in particular.