Inclusion criteria  Participant must fulfil the following:  be 18 to 65 years of age reporting a pain duration of ≥ 3 months being able to communicate in Swedish having access to a computer, smartphone, and the internet in their home environment.  Exclusion criteria:  Participant may not  be injury or illness that require immediate assessment or different treatment, or is expected to progress significantly during the next 6 months taking unstable medication (i.e., changes in medication during the past 3 months or expected within the next 3 months) having received previous CBT treatment (including ACT) during the past 6 months havning severe psychiatric co-morbidity (e.g., high risk of suicide)