CodeSandbox is an online code editor that allows developers to create, share, and collaborate on web applications directly in the browser. It supports various programming languages and frameworks, including JavaScript, React, and Vue.js, making it a versatile tool for both beginners and experienced developers. With CodeSandbox, users can quickly prototype ideas, test code snippets, and work on projects without needing to set up a local development environment. The platform also offers features like live previews and version control, enhancing the coding experience and facilitating teamwork among developers.