JSON can look correct and still fail because of one missing quote, comma, brace, or bracket. JSON Validator checks whether the text follows JSON syntax so you can isolate formatting problems before debugging an API, configuration file, webhook, or data export at a deeper level.
Syntax validation answers only one question: “Is this valid JSON?” It does not confirm that required fields exist, values have the expected type, or the document satisfies a JSON Schema or application rule. A payload can therefore pass syntax validation and still be rejected by the system that consumes it.
How to use this tool
How JSON validation works
A parser reads the text according to JSON grammar. If the entire document can be parsed into permitted JSON values without illegal tokens or structural mismatches, it is syntactically valid.
How to use JSON Validator
- Paste the complete JSON document you want to check.
- Run the validator.
- If an error is reported, inspect the indicated area for syntax issues such as commas, quotation marks, braces, brackets, or invalid values.
- Correct the JSON and validate it again.
- Remember that syntactically valid JSON can still violate an API schema or application-specific rule.
Technical reference
JSON syntax and parser behavior should be interpreted against RFC 8259.
Examples
Valid object
The document is syntactically valid JSON.
Missing comma
The parser should report an error near the second property because a comma is required between members.
Trailing comma
Standard JSON rejects the trailing comma.
Unquoted key
Property names must be double-quoted in strict JSON.
Common use cases
- Debugging API payloads
- Checking configuration files
- Validating webhook bodies
- Testing JSON exports
- Finding missing commas
- Finding unmatched braces
Frequently asked questions
What does the JSON Validator check?
It checks whether the supplied text conforms to JSON syntax. A document can be syntactically valid while still violating an API schema or business rule.
What are common JSON syntax errors?
Common errors include single-quoted strings, trailing commas, missing commas, unmatched braces or brackets, unescaped quotation marks, comments, and JavaScript-only values such as undefined.
Is valid JSON the same as a valid API payload?
No. JSON syntax only defines the data format. An API can require specific fields, types, value ranges, or nesting that a syntax validator cannot infer.
Why can JSON fail because of quotation marks?
Strict JSON requires double quotes around property names and string values, and quotation marks inside a string must be escaped correctly.
Can whitespace make JSON invalid?
Whitespace between JSON tokens is generally allowed, but characters inside quoted strings are data. Problems are more often caused by syntax than ordinary indentation.