Instantly preview HTML, CSS, and JavaScript code in real time. Paste your code and see the live output instantly - no setup, no server, 100% browser-based.
Quick frontend tests shouldn't require spinning up a dev environment. When you need to verify a CSS animation, test a JavaScript function, or check a layout at a specific viewport width, this tool delivers instant results without an account or install.
It's a lightweight alternative to a full playground for users who just need a fast test environment: paste your code, watch it render, adjust the viewport if you need to check responsiveness, done.
This HTML, CSS, and JavaScript playground solves a simple developer need: write a snippet, see the output immediately, and iterate without project setup. The editor panes are powered by Monaco - the same editor engine behind VS Code - and the preview runs in a sandboxed iframe so scripts execute without touching the parent page.
Add your HTML markup in the editor to structure your content.
Write CSS to design and style your HTML elements.
Insert JavaScript to add logic, events, and interactivity.
View the real-time output instantly in the preview panel.
Test CSS animations and transitions.
Debug JavaScript snippets.
Prototype layout structure.
Preview Tailwind CSS utility classes by loading Tailwind's CDN script tag in the HTML pane first.
Check how a layout holds up at tablet or mobile widths.
Test a code snippet from a tutorial, Stack Overflow answer, or AI assistant before dropping it into a real project.
Work through a live-coding interview question where you need to show DOM output without setting up a project.
Best For
JavaScript
undefinedFunction();Preview Output
ReferenceError: undefinedFunction is not definedThe script runs inside a try/catch - the error message is appended to the preview body in red instead of failing silently, so you can see what broke without opening a separate console.
JavaScript (before)
function greet(name){return "Hello "+name;}JavaScript (after Prettify)
function greet(name) {
return "Hello " + name;
}Prettify reformats whichever pane is active - HTML, CSS, or JavaScript - with 2-space indentation. It only changes whitespace, not the code's behavior, and needs to be run once per pane.
Paste a snippet from a tutorial, Stack Overflow, or an AI assistant and confirm it actually renders and runs before copying it into your codebase.
Toggle between the desktop, tablet (768px), and mobile (375px) preview widths to catch responsive layout issues without resizing your browser window.
Work through a DOM-manipulation or layout question and show working output immediately, without setting up a local project first.
Paste the HTML + Tailwind export from the Animated Button Generator, or a background from the CSS Gradient Generator, to see it render before wiring it into your project.
Problem
Solution
This tool doesn't save or persist anything between visits - reloading the page or closing the tab clears all three panes. Copy your code out before navigating away if you need to keep it.
Problem
Solution
Prettify only reformats whichever tab is currently active (HTML, CSS, or JavaScript) - switch tabs and run it again to format the other two.
Problem
Solution
The preview iframe is sandboxed to allow scripts and modals (alert/confirm) only - form submissions, popups, and top-level navigation are blocked, so code that relies on those won't behave as it would on a real page.
Problem
Solution
There are only three panes - HTML, CSS, and JavaScript - with no support for additional files or a build step, so code that imports from other files or expects a bundler won't run here unchanged.
The preview also updates automatically about 600ms after you stop typing, but clicking Run re-renders immediately if you don't want to wait.
There's no dedicated library picker, but pasting a <script src="..."> or <link> tag into the HTML pane - Tailwind's play CDN script, for example - loads normally, since the sandbox only restricts navigation and popups, not resource loading.
Paste the HTML + Tailwind export from the Animated Button Generator, or a background from the CSS Gradient Generator, to see it render immediately.
Code in all three panes is lost on reload or when the tab closes - there's no local storage, account, or save feature.
There's no button to export the combined snippet or generate a shareable link - copy the code from each pane manually if you need to save or send it.
You get exactly one HTML pane, one CSS pane, and one JavaScript pane - there's no way to add additional files or split code across more panes.
Loading a library means manually adding its script or link tag inside the HTML pane - there's no built-in list of libraries to toggle on.
This tool is built for fast, throwaway snippet testing with zero setup. A full playground adds accounts, persistence, and project features this tool doesn't have.
| HTML CSS JS Live Preview | Full Playground (CodePen/JSFiddle-style) | |
|---|---|---|
| Setup | None - open the page and start typing | Usually requires an account for saving and sharing |
| Persistence | None - code clears on reload | Saved pens/projects tied to your account |
| Files | One HTML, one CSS, one JavaScript pane | Often supports multiple files and a build step |
| Sharing | Not available - copy code manually | Shareable links are a core feature |
Which should you use?
Reach for this tool when you just need to see whether a snippet works right now. Reach for a full playground when you need to save, share, or build something you'll come back to.
The most common questions are whether code is saved between visits and whether external libraries like Tailwind or Bootstrap can be loaded - both are covered below, along with what the sandbox actually restricts.
No. This tool doesn't persist your code between visits - closing the tab or reloading the page clears whatever you've written. If you want to keep a snippet, copy it out of the editor pane before navigating away.
There's no dedicated library picker, but you can load any CDN script or stylesheet by adding its <script src="..."> or <link> tag directly in the HTML pane - for example, Tailwind's play CDN script. The sandbox restricts things like top-level navigation and popups, not standard resource loading, so CDN-hosted scripts and stylesheets load normally.
Yes. The preview renders inside an iframe with a restricted sandbox: scripts can run and modals (alert/confirm) work, but the preview can't navigate the parent page, open popups, or submit forms outside itself. Runtime errors in your JavaScript are caught and printed directly in the preview instead of silently failing.
Yes. Use the viewport toggle above the preview to switch between desktop (full width), tablet (768px), and mobile (375px) - useful for checking media queries and responsive layouts without resizing your browser window.
Not currently - this tool is focused on quick edit-and-preview iteration rather than saving or sharing. Copy the code from each pane manually if you need to save it elsewhere.
CodePen and JSFiddle offer accounts, saved pens, sharable URLs, and multi-file projects with npm-style package support. This tool doesn't do any of that - no login, no saved history, no share links - which also means there's zero setup: open the page and start typing. It's built for quick, throwaway snippet testing, not for building or publishing a project. For anything you need to save, share, or revisit later, a full playground like CodePen is the better fit.
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