User testing is significant in application design as it provides critical insights into how real users interact with a product. By observing users’ experiences and collecting feedback, developers can identify usability issues and areas for improvement. This process enhances user satisfaction and boosts engagement by ensuring the application meets the needs and expectations of its audience. Moreover, incorporating user testing early in the design phase fosters a more user-centric approach, ultimately leading to a more successful product that resonates with its intended market.