A browser-based playground for writing and sharing HTML, CSS, and JavaScript.
CodePen lets you write front-end code in the browser and see the rendered result as you type, with no local setup. Public 'Pens' can be shared by URL or embedded, and the site doubles as a gallery of community demos.
A free tier covers public Pens; private Pens and some team features require a paid plan.
You can view and experiment without one, but saving Pens requires signing up.
Information and links are accurate as of the time of writing and may change. Always verify on the official site. This is an independent guide, not affiliated with the listed services.