["Journal of the Association for Information Science and Technology, EarlyView. ", "\nAbstract\nConsumer‐grade sleep‐tracking technologies (CSTs) have brought sleep into everyday data practices, reframing it from a clinical concern into a site of personal optimization and reflection. Yet existing taxonomies of sleep‐tracking often medicalize users and overlook the complexity of sleep‐tracking technologies. This paper presents SleepTax, a naturalistic, multifaceted taxonomy of sleep‐tracking technologies based on metadata from 350 consumer devices. Using faceted classification, it identifies five dimensions—user purpose, technological form, functionality, contextual mobility, and temporal mode—and 120 concepts to characterize sleep tracking “in the wild,” including 17 forms, 83 functionalities, and multiple engagement styles. We further operationalize SleepTax through a design map and demonstrate how this framework supports scenario‐building and speculative inquiry into the sociotechnical consequences that emerge across different personal informatics (PI) infrastructure configurations. Together, SleepTax and the design map form a bridge between classification and design, supporting both systematic description and speculative inquiry in information science, PI, and human–computer interaction (HCI).\n"]