The technology that enables the creation of responsive user interfaces is called CSS, specifically the Responsive Web Design (RWD) techniques. CSS allows developers to apply styles that adapt to various screen sizes and resolutions, enhancing user experience across different devices such as smartphones, tablets, and desktops. Utilizing media queries, developers can specify different layout and design rules based on the characteristics of the user's display. This adaptability ensures that content is accessible and visually appealing no matter the device, leading to better user engagement.