JSON Validator & Syntax Checker
Validate your JSON data against RFC 8259 standards, catch syntax errors instantly, and pin-point missing brackets or quotes.
What is a JSON Validator?
A JSON Validator checks whether your JSON string follows the official RFC 8259 data interchange format specification.
Even a small syntax issue—such as a missing double quote, a trailing comma, or an unescaped special character—can cause a JSON parser to fail. The validator provides the exact error position, line number, and a suggested fix.
How to Validate JSON Online?
Paste String
Paste your JSON payload or API response into the left text area.
Click Validate
Click Validate JSON. The tool tests the input with a real-time JavaScript parser.
Read Diagnostics
Review the success report for valid JSON, or the exact error line and character position for invalid JSON.
Strict JSON Rules (RFC 8259 Standard)
| Rule Category | Valid Syntax Example | Invalid Syntax Example |
|---|---|---|
| String Quotes | "name": "John" (Double quotes required) |
'name': 'John' (Single quotes are not allowed) |
| Trailing Commas | [1, 2, 3] |
[1, 2, 3,] (A comma after the last item is invalid) |
| Array Key-Value Pairs | [{"key": "val"}] (Object inside Array) |
["a", "b", "key": "val"] (A direct key-value pair in an array is invalid) |
| Object Keys | {"age": 25} |
{age: 25} (Unquoted keys are not allowed) |
JSON Validator & Syntax Checker features
- Available tool controls: Validate JSON.
- Input and option fields: Paste JSON to Validate:, Validation Report:.
Using JSON Validator & Syntax Checker in a development workflow
A validator can narrow down why a sample fails a syntax or rule check. Start with the complete input, inspect the first reported issue, and correct the source rather than only hiding the message. A pass means the checked rules were satisfied; it does not confirm business logic, compatibility, or security unless those checks are explicitly included.
Keep the input small while debugging
- Check braces, array order, and value types in the result before sending it to an API or saving it as a project file.
- Pay attention to these page fields: Paste JSON to Validate:, Validation Report:. Confirm which fields are inputs, options, or output areas before processing.
- The page exposes these relevant actions: Validate JSON. Choose only the action that matches the result you need.
- If this data feeds an API or build step, verify required keys and types against that interface’s schema.
Check the output before passing it on
Check nested values, arrays, nulls, and string escaping in the result. A payload that parses successfully still needs to match the API or schema that will consume it.
Frequently Asked Questions (FAQ)
JSON.parse() exception stack and position offset to calculate the input character's line and column numbers.