The primary benefit of adopting a mobile-first design approach is improved user experience. This strategy prioritizes designing for mobile devices before scaling up to larger screens, ensuring that websites and applications are optimized for smaller displays. By focusing on the mobile experience first, developers address essential functionalities like loading speed and navigation, which are critical for mobile users. As a result, this approach often leads to better conversion rates and higher user engagement, as the mobile experience is tailored to user behavior and needs.