Cognitive behavioral therapy for insomnia (CBT-I) is the treatment of choice for insomnia; however, it is not widely used due to a lack of experienced therapists and its relatively high clinical cost. Recently, Internet and mobile CBT-I have been developed to replace face-to-face CBT-I, and research on this topic has been increasing. In addition, attempts have been made to use wearable devices for sleep–wake estimation. Studies on digital CBT-I thus far have shown favorable treatment effects in general, but the problem of a high dropout rate has not been sufficiently improved. In addition, more sophisticated technology is needed to develop fully automated digital CBT-I. As part of efforts to maximize the treatment effectiveness of future insomnia patients, research and development of mobile and Internet CBT-I and improvement of sleep tracker accuracy and validation studies are needed.