JSON Validator
Trending 🔥Validate JSON syntax instantly
How to Use JSON Validator
- 1Paste your JSON
- 2Click Validate JSON
- 3See if it is valid or get the exact error location
- 4If valid, copy the formatted JSON output
About JSON Validator
JSON Validator checks whether your JSON string is syntactically valid. If valid, it shows the parsed and formatted JSON output. If invalid, it displays the exact error message with the position of the syntax error so you can locate and fix the issue quickly.
This tool is essential for debugging API responses, configuration files, data exports, environment variables, and any JSON-formatted data. A single misplaced comma, an unmatched bracket, or a stray trailing quote can break an entire JSON document — the validator pinpoints the problem instantly.
All validation runs in your browser using the native JSON.parse() function — the same engine your application uses. This means the validator catches exactly the same errors your code would encounter, making it a reliable debugging companion.
Key Features of JSON Validator
- Instant JSON syntax validation using the browser's native JSON.parse()
- Displays exact error message and position for invalid JSON
- Shows formatted, pretty-printed JSON output when valid
- Clear visual pass/fail indicator
- Works with any valid JSON value — objects, arrays, strings, numbers
- Works entirely in-browser — no server uploads
- One-click copy for the formatted output
- Handles large and deeply nested JSON documents
Examples
Validate an API response before parsing in code
Confirm that a copied API response is valid JSON before using it in your application.
Input
{"user":{"id":1,"name":"Alice"},"token":"abc123"}Output
Valid JSON ✓ — formatted output displayed
Debug a configuration file with a syntax error
Find the exact location of a syntax error in a malformed config file.
Input
{"host":"localhost","port":3000,}Output
Invalid JSON — SyntaxError: Unexpected token } at position 32 (trailing comma)
Common Use Cases
- Validating API response payloads before writing parsing code
- Checking JSON configuration files (package.json, tsconfig.json) for syntax errors
- Debugging webhook payloads that are failing to parse in your application
- Verifying data exports from databases or ETL pipelines
- Checking environment variables that contain JSON-encoded values
- Teaching JSON syntax by seeing clear, immediate error feedback
Troubleshooting
Trailing comma after the last element
Solution
JSON does not allow trailing commas. Remove the comma after the last property in an object or the last element in an array.
Single quotes used instead of double quotes
Solution
JSON requires double quotes for all strings and property names. Replace all single quotes with double quotes.
Unexpected end of JSON input
Solution
A bracket or brace is not closed. Check that every { has a matching }, every [ has a matching ], and all strings are properly closed.
Frequently Asked Questions
Does it fix invalid JSON?
No. The validator identifies the exact error but does not automatically repair the JSON. Use the error message to locate and fix the issue manually, then re-validate.
What errors are shown?
The exact JavaScript JSON.parse() error message is displayed, including the position where the syntax error was detected.
What is the most common JSON syntax error?
Trailing commas after the last property or array element are the most common mistake, followed by single-quoted strings and missing closing brackets.
Can it validate JSON Schema compliance?
This tool validates JSON syntax only. It does not check whether the data matches a JSON Schema. For schema validation, use a dedicated JSON Schema validator.
Does it support JSON5 or JSONC?
No. This tool validates strict RFC 8259 JSON. JSON5 features like comments, trailing commas, and unquoted keys will cause validation to fail.
Can I validate very large JSON files?
Yes. The validator uses the browser's native JSON.parse() which handles large files efficiently. Files over 10 MB may cause a brief delay.
Is my data sent to a server?
No. All validation is performed locally in your browser using JSON.parse(). Your JSON data never leaves your device.
Why does the error position not match my line number?
JSON.parse() reports the character position from the start of the string, not a line number. Count characters from the beginning, or use the formatted output view.