CodeSandbox is built for front-end and full-stack web development in the browser. It spins up a complete environment with Node.js, npm dependencies, and hot reload, so you can start a React, Vue, Svelte, or Next.js project without local setup. Templates cover most popular frameworks. You can import a GitHub repository and get a running preview in seconds.

The platform is especially useful for sharing reproducible bug reports, testing library behavior, and building quick demos for clients or teammates. Sandboxes can be embedded in documentation or blog posts. The free plan supports public projects, while paid plans add private sandboxes and more resources. For front-end work, it removes almost all of the friction between an idea and a running prototype.