The significance of responsive web design lies in its ability to provide an optimal viewing experience across a wide range of devices. By using fluid grids, flexible images, and media queries, responsive design adapts layouts to various screen sizes, enhancing usability. This approach improves accessibility, as users can navigate websites seamlessly, whether on desktops, tablets, or smartphones. Additionally, search engines favor responsive designs for better indexing, positively impacting SEO. Overall, responsive web design ensures that users have a consistent and engaging experience, contributing to higher satisfaction and retention rates.