This clinical trial with 276 patients with subacute or chronic back pain aims to investigate the effectiveness of the unguided digital therapeutic relevis for patients with subacute or chronic back pain. Inclusion criteria are: age ≥ 18 years, presence of subacute (6-12 weeks) or chronic (\>12 weeks) back pain, attested by a medical certificate (relevant ICD-10-GM diagnoses: M47.8x, M47.9x, M54.5, M54.8x, M54.9x, M51.0x, M51.1x, M51.2), impaired functional ability \[Oswestry Disability Index (ODI) ≥ 21\], consent to participation, sufficient knowledge of the German language. Exclusion criteria are: change in treatment of back pain in the past month, planned change in treatment of back pain in the next 3 months, prior use of other online programs/apps for back pain, history of back, hip or knee surgery in the past 6 months, history of more than one back surgery in lifetime, presence of a specific cause for back pain (e.g., fracture, infection, neuropathies \[except when due to disc prolapse\], axial spondyloarthritis), tumor or metastases, cauda equina syndrome, acute myocardial infarction, unstable coronary heart disease/angina pectoris or heart failure, acute thrombosis, manifest osteoporosis, acute fevers, rheumatic autoimmune diseases. Patients will be randomized and allocated to either an intervention group in a 1:1 ratio, in which they will receive access to relevis in addition to treatment as usual (TAU, n = 138), or to a control group, in which they will receive only TAU (n = 138). TAU is defined as any therapy prescribed or recommended by the GP or specialists (e. g. orthopedic surgeon, rheumatologists etc.) which may include physiotherapy, injections in the spine, drug therapy, orthesis, etc. (1,2). The primary endpoint will be the functional impairment, measured by the ODI, with three months post-allocation being the primary time point for assessment of effectiveness (T1). Six months post-allocation (T2) will be used as the follow-up assessment endpoint. Secondary endpoints will be depression, work and social functioning, pain intensity, and health-related quality of life.