JSON Parser
Online JSON Parser
OnlinePaste your JSON and click Validate. Valid input returns a formatted version with a character count in the status bar. Invalid input returns the exact error message from the browser's JSON parser — including the character position where parsing failed.
Free, fast, runs in your browser. No login needed.
Unexpected token ',' at position 45.The validator runs JSON.parse() against your input and reports the result. On success it reformats the JSON with 2-space indentation. On failure it returns the raw error thrown by the JavaScript engine.
Error messages come directly from the browser runtime, so they're precise about position but phrased differently across engines. Chrome's V8 says Unexpected token ',' at position 45; Firefox's SpiderMonkey uses slightly different wording. Both point to the right location.
Common causes of invalid JSON:
{"a": 1,} is invalid. JSON does not allow trailing commas; JavaScript does.{'key': 'value'} fails. JSON requires double quotes throughout.{key: "value"} is JavaScript object syntax, not JSON.// line and /* block */ are not valid JSON.undefined, NaN, and Infinity have no JSON equivalent. Use null instead.0x1F is valid JavaScript but not JSON. Write decimal integers.What this tool does not validate: JSON Schema conformance — types, required fields, enum values, minimum/maximum. It only checks syntax. For schema-level checks, use the JSON Schema Generator on this site.
No size limit is enforced. Multi-megabyte JSON objects validate without issues; JSON.parse() handles them more efficiently than the textarea does at very large sizes.
Yes, free with no usage limits. No account or API key required.
Yes. The error message comes directly from the browser's JSON.parse() implementation, which includes the character position where parsing failed.
Trailing commas, single-quoted strings, unquoted keys, JavaScript-style comments, bare undefined/NaN/Infinity, hex literals, and any other deviation from the JSON spec.
No — this tool only checks syntax. It verifies that your input is a valid JSON string, not that it conforms to a particular schema. For schema validation, use the JSON Schema Generator on this site.
JSON validation answers "is this valid JSON?" — purely a syntax check. JSON Schema validation answers "does this JSON match a defined structure?" — types, required keys, value constraints. Both are separate operations.
No limit is enforced. Multi-megabyte inputs validate fine. Above roughly 5 MB the textarea may be slow to type in, but the validation itself completes without issues.