JavaScript Validator

Check JavaScript for syntax errors, live as you type, using your browser's own engine.

Runs in your browser, nothing sent

javascript-validator-linteryour input stays here

JavaScript

function greet(name) {
  return "Hello, " + name;
}

No syntax errors found.

Checks for syntax errors only, using your browser's own JavaScript engine — your code is parsed but never executed, and this isn't a style linter like ESLint (no rules about unused variables, missing semicolons, etc.). Runs entirely in your browser; nothing you type is sent anywhere.

Need the opposite? JavaScript Tester

What is JavaScript Validator?

Paste JavaScript and this tool checks it for syntax errors using your browser's own JavaScript engine. Your code is parsed but never executed. It's a quick syntax check, not a style linter like ESLint.

How to Use the JavaScript Validator

1
Paste the JavaScript: Enter the code you want checked for syntax errors.
2
Read the Result Instantly: Any syntax error, with its message and position, appears automatically as you type.
3
Fix and Recheck: Adjust the flagged line and watch the check update live.

How It Works

The pasted code is handed to the `Function` constructor, which parses it into a callable function but never calls it. Parsing alone is enough to surface a syntax error, since the JavaScript engine has to fully understand the code's grammar before it can build a function from it. If parsing fails, the engine's own error message and position are shown; if it succeeds, the function is discarded without ever being invoked.

What It Catches

Pure syntax errors: invalid grammar the engine can't parse at all. Example of invalid input: const total = (price * ; A dangling operator with no right-hand operand is a syntax error, and the tool flags it immediately without needing to run the code. What it won't catch: logic errors, undefined variables that only fail at runtime, or style issues like unused variables and inconsistent naming. Those require either running the code or a real linter like ESLint, neither of which this tool does.

FAQs

Frequently Asked Questions

Common questions about JavaScript Validator.

No, it only parses the code to check for syntax errors, using JavaScript's own Function constructor, which never executes the code unless the resulting function is called (which this tool never does).

No, that's the job of a linter like ESLint. This only checks whether the code is syntactically valid JavaScript.

Yes. The Function constructor only parses the code into a callable function; it's never invoked, so no statement inside it, including a fetch call, ever actually runs.

Yes, Bytelify's JavaScript Validator is free with no account or sign-up required.

No. The check runs entirely client-side using your browser's own JavaScript engine, so nothing you paste is sent anywhere.