In short: A responsive website adapts layout, content and controls to different screen sizes and device capabilities while keeping the same basic URL.
How I use a responsive website in practice
I test it with real content and devices, not only in a design. I look at first impression, readability, information order, error states and the ability to go back. Observing several people often reveals a more specific problem than a long team debate.
What to watch
A good-looking output is not automatically usable. A responsive website can meet an aesthetic goal while hiding important information, slowing the page or making controls difficult. Also beware testing only on a large monitor with ideal content.
Questions for decisions
- What task should the person complete on the page?
- Where might they hesitate, make an error or lose context?
- Does the solution work on mobile, with a keyboard and on a slow network?
- What signal will show that the change really helped?