Code Playground
Edit HTML, CSS and JavaScript together and see the page they make.
Processing: This tool runs entirely in your browser. Your input and any file you open stay on your device — nothing is uploaded to a server.
How to use the code playground
- Write HTML, CSS and JavaScript in the three panes.
- Press Run, and read the console for anything logged.
- Download the single HTML file to keep or share it.
About this tool
Three panes and a result: the arrangement every front-end developer already has in muscle memory. This one runs entirely in your browser with no account, no saved projects and no server involved, which makes it useful for the case those services are awkward for — trying something quickly, or on a machine that is not yours.
Everything can be downloaded as a single self-contained HTML file, which is worth more than it sounds: a page with its styles and script inline opens anywhere, needs no build step, and is the simplest way to hand someone a working demonstration.
The result runs in a sandboxed frame with `allow-scripts` and deliberately without `allow-same-origin`. Those two together let the frame reach back into the page that hosts it, its storage and its cookies — granting both is the standard way a sandbox gets quietly undone, and it is a common mistake in tools of this kind. Without same-origin the frame has an opaque origin: your code runs, and can see nothing of the page around it.
Nothing is saved between visits, and nothing about the code leaves the tab. The trade is that closing the page loses the work, so download anything worth keeping.
Common uses
- Building a small demonstration to hand to someone.
- Trying an idea end to end before putting it in a project.
- Working on a machine where you cannot install anything.
Frequently asked questions
- Is my work saved between visits?
- No. Nothing is stored, so download the HTML file if you want to keep it. That is the trade for a tool with no account and no server.
- What does the download contain?
- One self-contained HTML file with the styles and script inline, which opens anywhere without a build step.
- Can the code reach this page?
- No. It runs in a frame sandboxed without same-origin access, so it cannot touch this page, its storage or its cookies.
Related tools
HTML Live Editor
Write HTML and see it render as you type, in a sandboxed frame.
CSS Live Editor
Write CSS against a fixed piece of markup and see the result as you type.
JavaScript Playground
Run JavaScript in a sandboxed frame and read the console output on the page.
HTML Formatter & Minifier
Indent messy or minified HTML so it can be read, or strip it back down to one line.