There is increasing interest in digital mental health interventions that can provide effective and accessible care to entire populations. A comparably new approach with much potential to be a treatment for a wide range of mental health disorders is acceptance and commitment therapy (ACT). Researchers have examined the effectiveness of both, traditional ACT and digital ACT (iACT), with promising results, but with little focus on understanding the design of iACT interventions and how design features affected intervention effectiveness. Thus, we present a protocol for a scoping review to explore and define the emerging field of iACT, and to identify functionalities associated with iACT. In understanding how iACT interventions are delivered, we can address future design and research opportunities to expand the field of digital mental health interventions.