This research focuses on developing LegitCheck's website interface by applying the Parallax Scrolling Effect technique, which is considered as a potential solution to support the startup's promotional strategy. LegitCheck, as a startup that needs an effective way to introduce its services and business concept to consumers and brands, requires a website that can serve as an attractive promotional medium as well as a comprehensive information center. The purpose of this research is to examine the effectiveness of the Parallax Scrolling Effect technique compared to a website without the effect in increasing the effectiveness of the LegitCheck website as a promotional tool. The research method used includes the design and implementation of the Parallax Scrolling Effect technique on the LegitCheck website, followed by evaluation using the A/B testing method. The results showed that the implementation of the Parallax Scrolling Effect technique provided significant benefits, including improved information accuracy, service quality, user satisfaction, and company net profit. Although there are constraints related to page loading speed, the majority of respondents prefer websites with Parallax Scrolling Effect because it provides a more interactive and engaging experience. The implication of this study is that the use of Parallax Scrolling Effect can be an effective strategy for startups such as LegitCheck to increase interaction with users, strengthen brand image, and increase the effectiveness of the website as a promotional tool, although it is necessary to pay attention to technical aspects such as page loading speed to minimize potential disruptions to the user experience.