JavaScript Live Tester

The JavaScript Live Tester is a free online tool that lets you write, run, and debug JavaScript code snippets directly in your browser. It captures console.log, console.error, console.warn, console.table, and other console outputs, displaying them in a real-time output panel. No installation or setup is required — just type your code and hit Run.

The tool runs your code in the browser's native JavaScript engine, which means it supports all modern ECMAScript features including ES6+ arrow functions, classes, template literals, destructuring, spread/rest operators, async/await, Promises, generators, and more. The actual feature set depends on your browser — Chrome and Edge typically support the latest JS features.

Yes! Your code is automatically saved to your browser's localStorage. If you close the tab or refresh the page, your last code snippet will be restored. Clicking "Clear All" will remove the saved code. Note that localStorage is per-browser and per-device — your code won't sync across different devices.

Yes. Your code runs in the same browser context as the page, so you have full access to the DOM, window, document, fetch, localStorage, and all other browser APIs. This makes the tool great for testing DOM manipulation, API calls, and interactive code. However, be cautious — infinite loops will freeze the browser tab.

While this tool doesn't offer full step-through debugging like browser DevTools, you can effectively debug by using console.log() to inspect variable values, console.table() for tabular data visualization, and console.error() to highlight issues. Syntax errors and runtime exceptions are automatically caught and displayed with detailed stack traces in the output panel. For advanced debugging, open your browser's Developer Tools (F12).

Yes! Press Ctrl + Enter (or ⌘Cmd + Enter on macOS) to instantly run your code without clicking the Run button. The Tab key also inserts 2 spaces for indentation within the editor.

Since the code runs synchronously on the main thread, an infinite loop will freeze the browser tab. If this happens, you'll need to close the tab or use the browser's task manager to end the process. Always double-check loops and recursive functions before running. For long-running asynchronous operations (like setTimeout or fetch), the output panel will continue capturing console output as it arrives.