Abstract: Informal caregivers play a vital role in supporting individuals with chronic illnesses, disabilities, or age-related needs. This study aimed to develop and evaluate the design and content in an internet-based support program tailored to the needs of informal caregivers in Sweden. Utilizing the Delphi method, a panel of experts, including caregivers and caregiver advocates, provided iterative feedback on the program's design and content. The resulting prototype with eligibility, structured over 14 weeks, integrates cognitive behavioral therapy (CBT) and acceptance and commitment therapy (ACT) to address psychological well-being, stress management, and practical caregiving challenges. Key findings highlight the importance of accessible, flexible, and comprehensive support systems to enhance caregivers' quality of life and caregiving efficacy. The study underscores the need for continued research and development of digital support interventions to meet the diverse needs of informal caregivers.