Key features of a responsive mobile application include adaptability across various screen sizes, intuitive user interfaces, and optimal performance regardless of the device used. Such applications use flexible layouts and scalable images to ensure functionality on smartphones, tablets, and desktops. They often employ adaptive design techniques, adjusting content based on user behavior and preferences. This approach not only improves user experience but also enhances accessibility, leading to increased user engagement. Overall, responsive design is essential for modern mobile applications, given the diverse range of devices in use today.