The thesis aims to design a user-friendly and efficient web application for car rental services that can solve the challenges faced by small and medium-sized car rental companies in Debrecen, Hungary. It also aims to incorporate modern features such as real-time availability checks, personalized suggestions, and dynamic pricing algorithms to enhance the user experience. The study includes a user testing study to evaluate the efficiency of the online application, and it is expected to improve the competitiveness of local car rental businesses and contribute to the growth of the tourism industry in Debrecen. Overall, the research is a valuable contribution to the field of web development and online booking systems in the car rental industry.