Caregivers of people with heart failure experience a lack of support from health care in their caring role. They often want to become more involved in care, receive education and have the opportunity to share experiences with other caregivers. Objectives and hypothesis: Our hypothesis is that an internet-based support program that is developed in collaboration with caregivers of people with heart failure will increase preparedness to care (Preparedness for Caregiving Scale). We will also evaluate the effects of the support program on the experiences of caring including positive experiences and the impact of care on health and lifestyle (Caregiver Competence Scale, Rewards of Caregiving Scale, Heart Failure-Caregiver Questionnaire) and their management of heart failure (knowledge of heart failure, support for heart failure self-care and perceived control over heart disease). We will also explore if the patients' healthcare consumption is altered when caregivers receive more support. Method: The project is a randomized controlled study where 300 caregivers from four health care regions will be randomised to either receive a support program via 1177 care guide or to a control group waiting list who receive standard support from health care and municipalities. After the termination of the study participants in the control group will also be offered access to the support program. Data will be collected with questionnaires at baseline and after 3 and 6 months. A process evaluation with semi-structured interviews to describe the relatives' experiences of using the program with be conducted. Relevance: Caregivers have been involved in all stages of the development of the Internet-based support program. The evaluation focuses on both the effects of the intervention and factors that affect implementation and equality. Caregiver support that is delivered through 1177 care guide enables a more equal, efficient and accessible support for caregivers.