Background: Providing informal care can be experienced as stressful and lead to caregiver burden. Internet-based interventions, a specific form of eHealth, have proven to be a good option to support informal caregivers. SOSteniamoci, an internetbased intervention already tested in Lithuania, was translated and adapted for Italian caregivers. Objective: As many novel eHealth solutions have been rejected by end-users due to usability problems, we aimed to evaluate the usability of the adapted platform, using a computer-based prototype. Methods: The following methods and metrics were applied: 1. task analysis, using audio and video recordings that included three usability metrics: task completion rate, frequency of errors, and frequency of help requests; 2. the system usability scale (SUS); and 3. a semi-structured interview to collect additional data about the system's design and overall satisfaction. Results: Ten informal caregivers (60% female; age M= 47.8, SD = 15.21) provided insights and suggestions for increasing the usability of the platform. The platform was considered satisfactory, with a mean score on the SUS of 75 (SD = 13.07) out of 100. The task analysis measurements highlighted difficulties in how to log in to the platform, understanding what the intervention is about, and texting the therapist. The same difficulties were also mentioned during the post-experience interview. Thus, improvements were subsequently made to enhance users' experience when navigating the platform. Finally, the platform overall was found to be intuitive and friendly, and the contents were appreciated. Conclusion: To maintain participants' engagement and prevent drop-out, it is crucial to test the usability of internet-based interventions. Even though the platform proved to be user-friendly, intuitive and easy to use, several enhancements were implemented based on participants' feedback. Thus, the usability of internet-based interventions should be tested, and end-users must be involved in the development process of such solutions.