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Free developer tool

JavaScript Compiler

Write, test, and run JavaScript instantly in a safe sandbox, right in your browser. Type your code on the left, click Run Code, and see the output or errors on the right.

Working field

Write your JavaScript code and run it.

Code Editor

Result

Your console output appears here.

Your output will show here once you write some code and click Run Code.

This tool is best for quickly testing snippets, learning JavaScript, and debugging logic.

Free Online JavaScript Compiler & JS Runner

Write, test, and run JavaScript instantly without installing any software. This tool keeps the workflow simple: write and run on the left, supporting content below, and the sidebar on the left for popular and related tools.

Instant execution

Run your JavaScript right in the browser with zero setup and lightning-fast speed.

Safe sandbox

Code runs in an isolated iframe, keeping your device and data secure.

Modern syntax

Supports ES6 and beyond, including arrow functions, classes, and async/await.

Private by design

Everything runs in your browser, so your code never leaves your device.

How it works

  1. Type your JavaScript in the editor, or click Sample Code to start.
  2. Click Run Code to execute it safely inside the sandbox.
  3. Read the console output or any errors in the result panel on the right.
  4. Use Copy Code to grab your script, or Clear to start over.

Best practices

  • Use console.log() to print values you want to inspect.
  • Test small snippets first before running larger scripts.
  • Unminify compressed code before debugging it here.
  • Avoid restricted browser APIs inside the sandbox.
  • Keep a backup of important code outside the editor.
  • Minify your final script before using it in production.

Frequently asked questions

Can I run any JavaScript code here?

Yes. The JS compiler supports most modern JavaScript code. However, some advanced browser APIs may be restricted due to the secure sandboxed environment.

Is my code saved on your servers?

No. All code execution happens locally in your browser. We do not store, share, or even see the code you write.

How can I make my code production-ready?

After testing your code in the runner, use a JS minification tool to remove whitespace and comments, making the file size smaller for your website.

What should I do if I have a minified script to test?

First use a JS unminifier to make the code readable, which makes it much easier to debug errors in the compiler.

Does this JS compiler support ES6 features?

Yes. It fully supports modern standards like arrow functions, classes, let/const, and template literals.

Can I use this on a mobile phone?

Absolutely. The editor is fully responsive and optimized for coding on tablets and smartphones.

Why am I getting a sandbox error?

This usually happens if your code tries to access restricted browser features like cookies or certain cross-origin resources for security reasons.

Is there a limit on script length?

There is no hard limit, but very large scripts may slow down your browser's performance during execution.

How do I see the output of my code?

Any console.log() output or errors will appear instantly in the result panel beside the code editor.

Is this tool really 100% free?

Yes. All our developer tools are free to use with no hidden costs, ads, or sign-ups required.

Need more developer tools? Compress your script for production with the JS Minifier tool, or make a compressed script readable again with the JS Unminifier tool.