JavaScript Validator
Paste a snippet into this free JavaScript validator to check syntax without running the code. It uses the Acorn parser to report the exact line and column of the first syntax error - useful for students and for sanitizing snippets before sharing.
Security matters: many online “JS runners” execute untrusted code. CodingFormatter only parses. Choose module or script source type and an ECMAScript version in Options, then Validate. Your source never leaves the browser.
Input
Paste or type your content here…
Output
Your result will appear here
Frequently Asked Questions
Does this run my JavaScript?
Never. We only parse to an AST with Acorn. There is no eval, no Function constructor, and no iframe execution.
Will it catch logic bugs?
No - only syntax errors (missing braces, invalid tokens, etc.). Unit tests still matter for behavior.
Can I validate TypeScript?
TypeScript-specific syntax is not supported. Strip types or use a TS-aware tool for .ts files.
Module vs script mode?
Module allows import/export. Script mode matches classic <script> tags without module semantics.