What does a responsive layout use to adapt to different screen sizes?

A responsive layout primarily uses media queries in CSS to adapt to different screen sizes. Media queries enable web developers to apply specific styles based on the characteristics of the device being used, such as width, height, orientation, and resolution. By utilizing media queries, stylesheets can include rules that modify layout elements, text sizes, images, and other components to ensure optimal viewing and interaction, whether on a desktop, tablet, or mobile phone.

This approach is essential for creating a fluid and adaptable user experience, as it allows for targeted styling that can change based on the screen's dimensions. By defining different rules for various breakpoints, designers can prevent the need to create separate mobile and desktop versions of a website, thereby improving efficiency and maintaining consistency across devices.

While other options such as JavaScript and responsive frameworks can contribute to creating a responsive design, the core mechanism for changing styles based on screen size rests with media queries in CSS. Static design principles, on the other hand, do not offer flexibility for varying screen sizes, making them less suitable for modern web development where responsive design is a fundamental requirement.