JSON Validator

What makes JSON valid?

A valid JSON document is exactly one value: an object, an array, a string, a number, true, false or null. Strings use double quotes. Object keys are strings. Numbers follow the JSON grammar — no leading zeros, no hexadecimal, no NaN or Infinity.

There are no comments, no trailing commas and no single quotes. Anything a JavaScript engine would accept in source code but the JSON grammar does not is a syntax error.

How to validate JSON

• Paste, upload or drop your document into the editor.
• The verdict updates as you type — a green badge for valid JSON, a red panel with line and column for errors.
• Use “Go to line” to jump the cursor straight to the problem.
• Fix the issue, or apply the suggested repair when Jsonviewpro can determine one safely.

Common JSON errors and how to fix them

• Trailing comma — remove the comma after the last item in an object or array.
• Single quotes — JSON strings must use double quotes.
• Unquoted keys — every property name needs double quotes.
• Comments — // and /* */ are not part of JSON; strip them or use JSONC in an editor that supports it.
• Python or JavaScript literals — replace True, False, None, undefined and NaN with true, false and null.
• Unterminated string — a quote was opened but never closed, often after an unescaped backslash.
• Missing comma — two values sit next to each other with no separator.

Validating against a JSON Schema

Syntax validity is only half the question. Schema validation checks that a document has the fields your system expects, of the right types, within the right ranges. Paste a schema and Jsonviewpro validates your document against it in your browser, reporting each violation with its exact path.

If you do not have a schema yet, the JSON Schema generator can infer a first draft from a sample document.