JSON Validator
Validate JSON syntax and check for errors
JSON Input
Validation Result
What Is a JSON Validator?
JSON has strict syntax rules. Trailing commas, single quotes, unquoted keys, and missing brackets all make it invalid. A validator checks whether your text is well-formed JSON according to the JSON specification. If there's an error, it reports the location and the problem.
This tool uses JSON.parse() in your browser. Valid input produces a success message; invalid input shows the parse error. No data is sent to a server.
How to Use This Tool
Paste or Upload
Paste your JSON into the left editor or upload a file. Use Valid Sample or Invalid Sample to see both outcomes.
Check the Result
The right panel shows Valid or Invalid, plus any error details. The badge at the top indicates the status at a glance.
Fix and Recheck
If invalid, fix the reported issue and the validator updates automatically. Use Copy to grab the result. For formatted output, try the JSON Formatter.
Where JSON Validation Helps
Most developers need validation when reading API responses. You send a request through Postman or curl, and the response might be invalid—truncated, malformed, or wrapped in HTML. Pasting it here quickly tells you if the JSON is well-formed before you write parsing logic. For pulling out specific values from valid JSON, the JSON Path tool works well alongside this.
Config files like package.json or tsconfig.json with a typo can break builds. Running them through here catches syntax errors before deployment. Database exports, webhook payloads, and log entries that claim to be JSON often need validation too. If you need to format valid JSON for readability, use the JSON Formatter.
JSON Validation Examples
Valid JSON follows strict syntax. Here are telecom-themed examples:
Valid JSON (subscriber record)
Invalid JSON (unquoted key, trailing comma)
Use Valid Sample or Invalid Sample above to load these into the editor.
Common JSON Errors
Trailing commas are the most frequent mistake. {"a": 1,} is invalid. So is [1, 2, 3,]. Property names must be double-quoted; {a: 1} fails. Single quotes for strings are not allowed. The JSON.parse() documentation lists what's accepted.
This validator checks syntax only. It does not validate against a schema (e.g. required fields, data types). For that, use the JSON Schema Generator to create a schema, then validate elsewhere. The JSON Schema site has more on schema validation.
Frequently Asked Questions
Is my JSON sent anywhere?
No. Validation runs in your browser. Nothing is uploaded.
What if the error message is unclear?
JavaScript's parse errors can be cryptic. Look at the line and column number. Common fixes: remove trailing commas, use double quotes for keys and strings, check for missing } or ].
Does this support JSON5 or JSONC?
No. It follows strict JSON. Extensions like JSON5 (comments, trailing commas) or JSONC will fail here.
Can I validate a schema?
This tool validates syntax only. For schema validation, generate a schema with the JSON Schema Generator and use a library or another tool that supports JSON Schema.
Why does my API return invalid JSON?
Sometimes the response is truncated, has a BOM, or includes non-JSON text (e.g. error HTML). Check the raw response in Postman or DevTools. The String to JSON tool can help with escaped strings.
Related Tools
For a deeper look at JSON, see MDN's JSON guide and JSON.parse(). The formal spec is RFC 8259. The JSON specification at json.org defines the grammar. For schema validation, see JSON Schema.