Mobile First Design is an approach to web development that prioritizes designing for mobile devices before scaling up to larger screens like tablets and desktops. This method recognizes that many users access websites primarily through their smartphones, so it focuses on creating a seamless experience for these smaller screens first. By starting with mobile, designers can ensure that essential features are easily accessible and that the layout is user-friendly. Once the mobile version is complete, designers can then enhance the site for larger screens, adding more complex features and content. This strategy not only improves usability but also helps in optimizing performance, as it encourages a more streamlined design that caters to the needs of mobile users first.