JSON Validator
Validate JSON syntax and inspect structure with detailed error reporting.
Processed locally in your browserCheck whether your JSON is valid and inspect its structure with this free online JSON validator.
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How to Use
Check whether your JSON is valid and inspect its structure with this free online JSON validator.
- Paste or upload your JSON. Enter raw JSON text into the input field or upload a .json file. Validation runs automatically as you type.
- Read the result. A green banner means your JSON is valid; a red banner shows the exact error message with line and column numbers so you can jump to the problem.
- Inspect the structure. When JSON is valid the tool displays key count, nesting depth, and a breakdown of value types — useful for verifying API responses or config files.
- Try auto-repair. If validation fails, click the Repair button. The tool attempts common fixes: removing trailing commas, quoting unquoted keys, replacing single quotes, and stripping comments.
- Copy the validated output. Once your JSON passes validation, copy it to the clipboard for use in your code or configuration.
All processing happens in your browser — no data leaves your device. The validator follows the strict RFC 8259 specification, ensuring your JSON works with any standards-compliant parser.
After fixing validation errors, use the Diff Checker to compare your original and corrected JSON and verify exactly what changed.
Features
- ✓Syntax validation with error details
- ✓Line and column error position
- ✓Structure analysis (depth, keys, types)
- ✓File upload support
- ✓Copy validated JSON
- ✓Real-time validation
Frequently Asked Questions
- What is valid JSON?
- Valid JSON is text that strictly conforms to the JSON specification (RFC 8259). A JSON validator checks that strings are double-quoted, numbers have no leading zeros, keys in objects are unique strings, and values are one of the six allowed types: string, number, object, array, boolean, or null.
- What are the most common JSON errors?
- The most frequent errors caught by a JSON validator include trailing commas after the last item in an object or array, single-quoted strings instead of double quotes, missing commas between key-value pairs, and unescaped special characters inside strings. Mismatched or missing brackets and braces are also very common.
- What is the difference between a JSON object and a JavaScript object?
- A JSON object is a strict text format derived from JavaScript, but it requires double-quoted keys and does not support functions, undefined values, or comments. A JavaScript object is a runtime data structure that is much more flexible. A JSON validator checks only the JSON subset, not general JavaScript syntax.
- How do I fix invalid JSON?
- Start by running the JSON through a validator to get the exact line and column of the error. Common fixes include replacing single quotes with double quotes, removing trailing commas, adding missing colons, and escaping special characters like backslashes and newlines inside string values.
- What is strict JSON validation?
- Strict JSON validation means applying the full RFC 8259 specification with no extensions — no comments, no trailing commas, and no unquoted keys. This JSON validator uses strict mode to ensure your data will be parsed correctly by any standards-compliant JSON parser across any language or platform.