JavaScript Syntax Validator
Paste JavaScript code to check whether it is valid — complete with the reason if it is invalid and a component breakdown if it is valid. Everything is processed on your device.
Everything runs in your browser. Your data is never sent to our servers.
Example
Example Input
const x = (a, b) => a + ;
Example Output
✗ INVALID — Unexpected token (line 1)
How to Use
- 1Paste the JavaScript code you want to check into the input box.
- 2If the tool offers extra options (e.g. dialect, flags, or variant), set them as needed.
- 3Click Validate (or press Ctrl+Enter).
- 4Read the result badge — VALID, INVALID, or VALID with a warning — along with the details and the list of issues, if any.
About JavaScript Syntax Validator
JavaScript Syntax Validator parses your code with acorn (the same parser many build tools use) and reports the first syntax error with its line and column. The code is tried as both a module and a script, so top-level import/await and return are accepted.
This checks SYNTAX — it does not run the code and does not check logic or runtime errors — safe because there is no eval.
FAQ
Is my data sent to a server?
No. All validation runs in your browser with JavaScript. Nothing is uploaded, logged, or stored on our servers — safe for sensitive data.
How is this validator different from a parser or formatter?
A validator answers one question: is this input correct/valid? It returns a valid/invalid badge with the reason. A parser breaks input into its components, and a formatter tidies its layout. Use a validator when you just need to confirm something is sound before using it.