The importance of a mobile-first approach in web design lies in the shift in user behavior towards mobile devices for browsing and online activities. This strategy prioritizes the design and development of websites for mobile users before adapting them for desktop platforms. By focusing on mobile-first, designers ensure that websites are responsive, user-friendly, and optimized for smaller screens, improving accessibility and engagement. This approach enhances user experience and can positively impact search engine rankings as search engines increasingly favor mobile-optimized sites. Ultimately, a mobile-first strategy is essential for reaching and retaining a modern audience.