CodePen is a social development platform where you can write, test, and share HTML, CSS, and JavaScript snippets (“pens”) in the browser.
Yes. There’s a free plan for getting started, and Pro plans for private pens, assets hosting, collab mode, and more.
Absolutely. Share public links, embed a pen in articles, or export the code to use in your projects.
It ensures your interface adapts to every device, improving usability, performance, and accessibility.
Clarity, consistency, hierarchy, feedback, and inclusive design. Keep content readable and interactions predictable.