Paste your JSON into the editor above and errors are highlighted instantly as you type. The validator pinpoints the exact line and column of every syntax mistake and explains what went wrong in plain English — no cryptic parser messages.
Built on the same high-performance Web Worker parser that powers the JSON Beautifier, it handles files up to 25 MB without freezing your browser tab.
JSON (JavaScript Object Notation) is a lightweight data-interchange format. Validation checks that your text strictly conforms to RFC 8259 — the standard that defines valid JSON. A validator catches problems like trailing commas, mismatched brackets, unquoted keys, and invalid escape sequences before they cause runtime errors in your application.
{"a":1,})// line or /* block */ commentsundefined, NaN, and Infinity are JavaScript values, not valid JSONWhat makes JSON valid?
Valid JSON must follow RFC 8259: strings use double quotes, objects have key-value pairs separated by commas, arrays are comma-separated values in brackets, and supported value types are strings, numbers, booleans (true/false), null, objects, and arrays. Trailing commas, single quotes, and comments are not allowed.
Why is my JSON invalid even though it looks correct?
Common hidden issues include trailing commas after the last item in an object or array, smart quotes (“”) copied from a word processor instead of straight double quotes, invisible Unicode characters, or unescaped special characters inside strings. This validator highlights the exact line and column of the error.
Is my JSON sent to a server?
No. All validation happens locally in your browser using a Web Worker. Your data never leaves your device.