A quick HTML/CSS/JS sandbox
Edit HTML, CSS, and JavaScript in the three panels and see the result update instantly in the live preview - useful for quickly testing a snippet, prototyping a small component, or checking how a bit of markup renders without setting up a local project. The preview runs in a sandboxed iframe entirely in your browser; nothing is saved or sent anywhere.
Why changes appear instantly as you type
Every edit to any of the three panels rebuilds the preview document immediately and reloads it into the iframe - there's no save step or refresh button needed, which makes this well suited to quick iteration: tweak a CSS value, see the visual result immediately, adjust again.
Why the preview runs in a sandboxed iframe
Rendering your code inside an isolated iframe, rather than directly in the main page, keeps whatever you're testing contained - your experimental JavaScript can't accidentally interact with or break the editor page itself, which matters when you're deliberately testing unfamiliar or exploratory code.
Testing a component before adding it to a real project
Pasting a self-contained snippet you found or wrote - a CSS animation, a small interactive widget, a layout technique - into this sandbox lets you confirm it actually behaves as expected before copying it into a real codebase, without needing to spin up a local dev server just to check one snippet.