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HTML/CSS/JS Playground

Write and preview HTML, CSS, and JavaScript code in real-time

Web Dev Tools
Tip: Write your code in the editors and see live preview instantly. Your code is auto-saved to browser storage.

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What Is an HTML Playground?

An HTML playground is a browser-based editor that renders your HTML, CSS, and JavaScript together in a live preview. This tool gives you three tabbed panels, one for each language, and combines their content inside a preview iframe. Every keystroke updates that iframe, so you see the rendered page as you type.

All processing runs inside your browser. Your code is never sent to a server. JavaScript runs in a sandboxed iframe, which keeps the executed script separate from the rest of the page.

How the Live Preview Works

The editor takes the text from the HTML, CSS, and JavaScript tabs, stitches them into a single document, and loads that document into the preview iframe. When you change any tab, the tool rebuilds the document and reloads the frame. The result is a rendered view that tracks your edits without a manual save.

The Console panel captures output from inside the iframe. It listens for console.log calls, uncaught errors, and warnings, then prints them below the preview. This lets you debug scripts without opening browser dev tools.

  • Toggle the Console panel to read logged messages and script errors.
  • Click "Clear Console" to wipe the current output and start clean.
  • Click "Refresh Preview" to force the iframe to re-render from scratch.

Writing and Testing Code

Open Web Dev Tools and select "HTML/JS/CSS Playground". You land on three panels with a monospace font and a minimum editor height of 550px. The preview sits beside the editors at the same height and full width.

Here is the flow for a quick test:

  1. Type your markup in the HTML tab.
  2. Add rules in the CSS tab to style that markup.
  3. Write behavior in the JavaScript tab, then watch the preview update.
  4. Open the Console panel to check logs and catch errors.
  5. Click "Fullscreen Preview" when you want the rendered result to fill the window.

Press Escape or click the exit button to leave fullscreen and return to the split view. Your work saves to localStorage automatically, so it stays in place when you reload or come back later.

Importing and Exporting Files

The "Upload Files" button reads local files and drops their contents into the matching tab. It accepts .html , .htm , .css , and .js files, so you can pull existing work into the code playground for HTML without copy and paste.

The "Download" button bundles all three editors into a ZIP archive. That archive holds three files with standard names:

  • index.html for your markup
  • style.css for your styles
  • script.js for your JavaScript

The ZIP is built in your browser, so the export needs no upload step.

How This Differs From Other Tools

Many online editors focus on a single language or format your code without running it. This html code playground renders the combined output and captures runtime messages in one view. It differs from formatting and cleanup tools in a few ways:

  • It executes JavaScript in a sandboxed iframe, so you test behavior, not just layout.
  • It captures console output and errors inside the page, so you skip external dev tools for basic checks.
  • It exports a ready folder structure as a ZIP rather than a single blob of text.

If you only need to tidy markup, the HTML Beautifier or CSS Beautifier handle that. To shrink files before shipping, the HTML Minifier removes whitespace and comments. Use this editor when you want to run and see the result.

When to Use It

Reach for this editor when you want to prototype a component, reproduce a bug, or teach a concept with a working example. Because the preview updates as you type and the Console reports errors, the loop between writing and checking stays short.

  • Prototype a layout or interaction before moving it into a larger project.
  • Build a small reproduction to share a bug or a question.
  • Test a snippet from a tutorial and watch it run.
  • Experiment with CSS while reading logged values from your script.

FAQ

It is a browser-based editor with three tabs for HTML, CSS, and JavaScript. The tool merges the content of all three tabs into one document and loads it into a preview iframe. That frame renders your page as you type, so you write code and view the rendered result side by side without a manual build step.

No. All processing runs inside your browser, and no code leaves your machine. The preview, the console capture, and the ZIP export are all built locally. Your work is stored in browser localStorage so it persists between sessions. Clearing your browser data removes that saved work, since nothing is kept anywhere else.

Yes. The Console panel listens to the preview iframe and captures console.log messages along with uncaught errors and warnings. It prints them below the preview, up to a scrolling panel height. This means you can read logged values and spot broken scripts without opening the browser dev tools. Click "Clear Console" to reset the output.

Yes. Auto-save writes the content of all three tabs to browser localStorage as you edit. When you reopen the page in the same browser, your code loads back into the tabs. The catch is that this storage is tied to that browser on that device. Clearing site data or using a different browser will not show the saved work.

The "Upload Files" button accepts .html , .htm , .css , and .js files. When you pick a file, the tool reads its text and places it in the matching editor tab. HTML files go to the HTML tab, styles to the CSS tab, and scripts to the JavaScript tab. This lets you continue existing work without pasting it by hand.

The "Download" button bundles your three editors into a ZIP archive built in your browser. Inside you get index.html , style.css , and script.js . The HTML file references the other two, so the folder works as a small project you can open locally or drop into a repository. Nothing is uploaded to create the archive.

A beautifier reformats your markup by adjusting indentation and line breaks, then returns the same code in a tidier shape. It does not run anything. This editor merges HTML, CSS, and JavaScript, executes the script in an iframe, and renders the output. Use the HTML Beautifier to clean formatting and this editor to run and view the result.

Fullscreen preview expands the iframe to fill the browser window and hides the editors. This helps when you want to check layout at a wider size or view a design without the split panels taking room. Press Escape or click the exit button to return to the split view, where your editors and code stay exactly as you left them.

Yes. The JavaScript tab runs inside the sandboxed preview iframe, so scripts that read or change the DOM act on the rendered document. Event handlers, timers, and element updates all work against the markup and styles you wrote in the other tabs. If a script logs values or throws an error, the Console panel reports it so you can trace what happened.

You can add link and script tags in the HTML tab that point to external URLs, and the preview iframe will try to load them like any browser. Loading depends on the remote source allowing it, so some assets may be blocked by their own settings. For local styling and behavior, use the CSS and JavaScript tabs, which are merged directly into the preview.

The preview normally rebuilds after each edit. If it stalls, click "Refresh Preview" to force the iframe to re-render from your current code. A refresh reloads the frame, which also resets any running timers or state your script created. If a script error is blocking output, open the Console panel to read the message and fix the line it points to.

Yes. Once a prototype looks right, run the markup through the HTML Minifier to reduce file size before shipping. For picking colors while you style, the online color selector gives you values to paste into the CSS tab. These pair well with the editing loop this page provides.