Code Snippet Playground – Live HTML, CSS & JS Preview
Three separate editors — HTML, CSS, and JavaScript — with a sandboxed live preview that updates in real time as you type. No run button, no backend, no signup. The perfect front-end prototyping tool for quick snippets.
Write snippets and watch preview update in real time.
Included Editor Panels
HTML Editor
Write or paste HTML markup with automatic tag and closing behavior.
CSS Editor
Add styles in a dedicated CSS panel applied live to your HTML output.
JavaScript Editor
Write JS logic that runs directly inside the sandboxed preview iframe.
Live Preview
Sandboxed iframe updates in real time as you type — no run button needed.
How to Use the Code Playground
Write your HTML
Type or paste HTML into the HTML editor panel. The preview updates instantly as you type.
Add CSS styles
Switch to the CSS panel and style your elements — changes apply live to the preview.
Add JavaScript
Open the JS panel to add interactivity. Scripts run inside a sandboxed iframe with no access to your page.
Load a sample
Click 'Load sample' to see a prebuilt demo with a styled card and click counter, then remix it.
What You Can Build and Test in This Playground
The playground is a sandboxed browser environment that executes real HTML, CSS, and JavaScript — the same languages the browser uses to render every website. Use it to prototype UI components without setting up a project, test a CSS layout or animation before copying it into production code, verify a JavaScript function works as expected, reproduce a bug from Stack Overflow to understand it, try out a CDN-hosted library like Chart.js or Alpine.js without installing anything, and share a minimal reproducible example when asking for help. It is especially useful for students and learners who want to experiment without configuring a local development environment. Add a Tailwind CSS CDN link in the HTML panel and you have a Tailwind prototyping environment in two seconds — no install, no build step, no configuration.
How the Sandbox Isolation Works
The live preview renders inside an<iframe> with thesandbox="allow-scripts" attribute. This means the preview can run JavaScript but cannot: read or write cookies, access localStorage of the parent page, submit forms, navigate the parent window, or make same-origin requests to the parent's domain. It is the same isolation model used by CodePen and JSFiddle. The consequence for you as a user: you cannot accidentally break your browser session by running bad code in the playground — the worst that can happen is the preview crashes, which you fix by editing the code. Cross-origin network requests (fetching from an external API) do work if the target server sends CORS headers. If you need to test fetch() calls, use a public API with CORS enabled or add the CDN library for mocking.
Frequently Asked Questions
- Is this a CodePen alternative?
- Yes. ToolMint's Code Snippet Playground provides the same HTML/CSS/JS split-pane live preview experience, entirely in your browser with no login required.
- Does the JavaScript run securely?
- Yes. The preview iframe is sandboxed with allow-scripts only — no cookies, no form submission, no same-origin access. Your page and the preview are fully isolated.
- Does the preview auto-update as I type?
- Yes. There is no Run button — the iframe re-renders as you type in any of the three editors.
- Can I load external libraries like jQuery or Tailwind?
- Yes. Add a script src or link rel=stylesheet tag in the HTML editor to pull in any CDN-hosted library.
- Is my code saved between sessions?
- The code is kept in memory while the tab is open. Refresh or close the tab to start fresh.
Related Tools
Python Code Editor
Run Python code directly in your browser using Pyodide (WebAssembly CPython) — no install, stdin simulation included.
JSON Formatter
Beautify, validate, minify, and convert JSON to XML, CSV, or YAML — with inline error location on parse failure.
Base64 Encoder/Decoder
Encode text or files (images, PDFs, binary) to Base64 and decode Base64 strings back to plain text — UTF-8 safe.
URL Encoder/Decoder
Encode URLs with 4 percent-encoding methods, decode with 3 methods, and parse any URL into its components.