The aim of this study was to compare a public health website with a commercial health website to identify differences in their interfaces. The goal was to explore whether there is a connection between information architecture and credibility. To address this, the research question posed was: Which factors affect the credibility of the interfaces in the public healthcare service “1177” and the private healthcare service “Kry”? Previous research in this field has highlighted that factors such as website structure, content, and usability play a crucial role in enhancing a website’s credibility. In this study, an interface analysis was conducted, and a heuristic evaluation was performed to identify differences. The public healthcare service “1177” achieved a higher score in the heuristic evaluation. However, this study shows that both public and commercial healthcare services achieved good usability results. The study’s theoretical framework is based on the Prominence-Interpretation Theory (PIT) and the Extended Prominence-Interpretation Theory (EPIT). According to these theories, an interface’s credibility increases when its usability is high. The identified differences between the two websites included variations in their structure and language.