What is responsive web design?

Responsive web design means a site automatically adjusts its layout, images, and text to fit whatever screen it's viewed on, phone, tablet, or desktop, without needing a separate mobile version.

It's built with flexible grids and code that respond to screen size rather than a fixed layout. Without it, a site built for desktop shows up broken, cramped, or hard to navigate on a phone, which is where most visitors are.