JavaScript Validator
Validate JavaScript syntax and check for errors
Input JavaScript
Validation Result
What is JavaScript Validator?
JavaScript Validator is a free online tool that checks your JavaScript code for syntax errors and validates it against JavaScript standards. Whether you're debugging code, learning JavaScript, or preparing code for production, our validator instantly tells you if your JavaScript is valid or where the errors are.
According to MDN Web Docs, JavaScript validation is crucial for catching errors early. Our validator follows JavaScript standards, so you can trust the results. Valid JavaScript gets a green badge, invalid JavaScript shows you exactly what's wrong.
Everything runs in your browser – your code never leaves your computer. Fast, secure, and completely free.
What Makes This Tool Different
Instant Validation
Paste your JavaScript and get results right away. Valid code gets a green badge, invalid code shows you exactly where the problem is.
Detailed Error Messages
When something's wrong, we tell you the exact line, column, and what went wrong. No guessing – you'll know exactly what to fix.
File Upload Support
Got a big file? Just upload it. No need to copy-paste those massive JavaScript files or libraries.
Sample Data
Try it out with sample data. We've got examples of valid JavaScript so you can see how it works.
Standards Compliant
We validate against JavaScript standards. If it passes here, it'll work in browsers, Node.js, or any JavaScript environment.
Syntax Highlighting
Nice syntax highlighting makes it easy to spot problems before you even validate. Visual feedback helps catch issues early.
How It Works
Paste or Upload JavaScript
Paste your JavaScript code into the left editor, or click "Upload" to load a file. You can also click "Sample" to see an example of valid JavaScript.
Automatic Validation
The validator automatically checks your JavaScript as you type. The right panel shows the validation result with a clear badge – green for valid, red for invalid. If there are errors, you'll see detailed error messages.
Fix and Verify
If your JavaScript is invalid, use the error messages to fix the issues. Common problems include missing semicolons, unclosed brackets, or syntax errors. Fix the errors and watch the validation status update in real-time.
When You'd Actually Use This
Code Review
Validate JavaScript before committing or deploying. Catch syntax errors early in development. Works great for code reviews or pre-deployment checks.
Learning JavaScript
New to JavaScript? Use the validator to check your work. Practice writing JavaScript and see if it's valid before using it in your projects.
Debugging
Getting runtime errors? Validate the JavaScript first. Our detailed error messages help you find syntax problems faster than trial and error.
Pre-Deployment Checks
Before deploying, validate your JavaScript files. One syntax error can break your entire application. Catch it early with our validator.
Common Questions
Is my JavaScript code stored?
Nope. Validation happens right in your browser using JavaScript. Your code never leaves your computer.
What makes JavaScript invalid?
Common issues include: missing semicolons, unclosed brackets or braces, syntax errors, undefined variables, or incorrect operators. Our validator catches all of these.
Does it validate ES6+ features?
Yes, we support modern JavaScript syntax including ES6+, async/await, arrow functions, classes, modules, and more. If it's valid JavaScript, we can validate it.
What JavaScript standards does it follow?
We follow the ECMAScript specification. If it validates here, it's valid JavaScript.
Can I validate large files?
Yes. Since validation happens in your browser, performance depends on your device. Small files validate instantly. Very large files (10MB+) might take a few seconds.
Why does my JavaScript show as invalid?
Check the error message – it tells you exactly what's wrong. Common fixes: add missing semicolons, close all brackets and braces, check for typos, and verify syntax is correct.
Other JavaScript Tools You Might Need
Validation is just one step. Here are other tools that work well together:
Need to learn more about JavaScript? Check out the comprehensive guide on MDN or the official ECMAScript specification.