Chronic pain constitutes an increasing health and social burden. More than 50% of patients with chronic pain report insomnia, and patients with comorbid insomnia often report stronger and widespread pain, compared to those who are sleeping well. Sleep disturbances are often considered a consequence to chronic pain. This means that insomnia is often overlooked or ineffectively managed with hypnotics or advice on sleep hygiene. Therefore, efficacious, easily accessible, and safe alternatives to the current pharmacological treatments for patients with chronic pain and insomnia are needed. Cognitive behavioral therapy for insomnia (CBT-I) is a cost-effective and safe treatment for insomnia and is recommended as first-line treatment. While highly efficacious, the challenge is to deliver CBT-I to those in need. The main barriers of face-to-face delivered CBT-I are availability of trained therapists, costs, as well as physical and geographical constraints. The primary aim of this randomized controlled clinical superiority trial is to investigate whether digitally-delivered CBT-I has a greater effect on insomnia and pain than digitally-delivered sleep hygiene education in patients with chronic pain and comorbid insomnia. Secondary objectives are to a) explore whether the pain-relieving effect is mediated by a change in physiological markers of sleep quality, b) whether health care cost and use of medications at 12 months are reduced after digital CBT-I, and c) to explore the effectiveness of digital CBT-I compared with sleep hygiene education on: 1. Physiological sleep metrics (recorded with ear EEG in subsample of 60 patients). 2. Self-reported sleep quality. 3. Quality of life. 4. Physical and mental health. 5. Thoughts and beliefs about sleep and pain.