The significance of responsive web design in modern websites is its ability to provide an optimal viewing experience across a range of devices. With users accessing websites on smartphones, tablets, and desktops, responsive design adjusts layout and content dynamically based on screen size. This adaptability improves navigation, readability, and overall user experience, which can enhance engagement and retention rates. Moreover, responsive design contributes positively to search engine optimization (SEO), as search engines prioritize mobile-friendly sites in search rankings. Ultimately, responsive web design is essential for meeting diverse user needs.