JavaScript Validator
Validate JavaScript syntax and check for errors
Input JavaScript
Validation Result
What Is the JavaScript Validator?
You've just deployed code and the page is broken — or you're trying to commit a JS file and the CI pipeline is failing. Before you spend another 30 minutes hunting for a missing semicolon or an unclosed bracket, paste your code here. The JavaScript Validator parses your JavaScript using the browser's own engine and tells you immediately whether it's valid or exactly where it fails. The ECMAScript specification defines what valid syntax looks like. For style and best-practice linting beyond syntax, ESLint is the go-to tool — and the ECMA-262 standard is the authoritative language reference. This tool only checks syntax, not runtime logic — but catching syntax errors before sharing or deploying code saves real time.
The parse happens inside this tab, so the script you are debugging is not uploaded and nothing in it is executed. Once it parses cleanly, tidy it with the JavaScript Formatter. For minifying, use JavaScript Minifier. For converting to TypeScript, use JavaScript to TypeScript.
How to Use This Tool
Paste or Upload
Drop the suspect script into the input pane, or pull in a .js or .txt file with Upload. Sample loads a short snippet to try, and Clear empties the pane.
Check the Result
The right panel shows VALID or INVALID and lists any syntax errors with line numbers.
Fix and Revalidate
Fix errors in the left panel. The result updates. For formatting valid code, use JavaScript Formatter.
JavaScript Validator Examples
Here are examples of valid and invalid JavaScript syntax.
Example: Valid subscriber code
Valid JavaScript (proper closing brace):
Example: Invalid (missing comma)
Invalid JavaScript (missing comma before closing brace):
When the JavaScript Validator Helps
Before committing code, deploying, or debugging runtime errors, validate syntax. Catches missing brackets, typos, and invalid constructs. The ECMAScript spec defines valid syntax. For linting style and best practices, use ESLint or Prettier. For JSX, use JSX Formatter which may report parse errors.
Frequently Asked Questions
Is my data private?
Yes. The syntax check is done by a parser running in this tab, and your source is not posted anywhere.
Validator vs Formatter?
Validator checks syntax only. Formatter reformats valid code for readability. Use both in sequence.
Does it support ES6+?
Yes. Modern JavaScript syntax is supported.
What about TypeScript?
This tool validates JavaScript. TypeScript has its own type checker. For JS to TS conversion, use JavaScript to TypeScript.
Does it catch logic errors?
No. It checks syntax only. Logic errors, undefined variables, and runtime issues require testing or a linter like ESLint. See MDN JavaScript Guide for language reference.