The significance of user interface (UI) design in applications lies in its impact on user experience. A well-designed UI ensures that applications are intuitive, visually appealing, and easy to navigate, which encourages user engagement and satisfaction. Effective UI design can enhance productivity by enabling users to accomplish tasks efficiently without confusion. It also influences brand perception; applications with polished interfaces are often seen as more trustworthy and professional. Therefore, investing in strong UI design is essential for application success.