JavaScript Validator

How the JavaScript Validator works

This tool checks JavaScript source for syntax errors by asking your browser's own JavaScript engine to parse the code (without ever executing it), using the same grammar engine that runs your web pages. That means the syntax errors reported here — unexpected tokens, unterminated strings, missing brackets, invalid declarations — are exactly what the browser would throw when it tries to load your script. A supplementary bracket and quote scanner cross-checks braces, parentheses, and string literals line-by-line so you can jump straight to unbalanced tokens even when the engine only reports an end-of-input error.

Use Script mode for regular JavaScript files, inline <script> tags, or CommonJS/Node code. Use Module mode when your snippet contains ES module syntax like import or export statements. Nothing you paste here ever leaves your browser — all parsing happens locally and instantly.