"Mobile First" is a design and development approach that prioritizes creating websites and applications for mobile devices before adapting them for larger screens like tablets and desktops. This strategy recognizes the growing number of users accessing the internet primarily through smartphones, ensuring that the user experience is optimized for smaller screens. By focusing on mobile devices first, designers and developers can streamline content and features, making them more accessible and user-friendly. This approach often leads to faster load times and improved performance, ultimately enhancing user satisfaction and engagement across all devices, including tablets and desktops.