Free JSON Validator Online - Syntax & Schema Validation
Validate JSON instantly and detect syntax errors before they break your API, config, or data pipeline. Our JSON Validator checks whether your JSON is structurally valid, highlights parsing issues, and helps you find problems such as missing commas, invalid quotes, and malformed objects. Paste your data below to validate it now, then use the formatter or minifier if you need to clean up the output.
Validate JSON syntax, check against JSON Schema (Draft 2020-12), and get instant error messages with exact line numbers. 100% free, runs in your browser.
Example data loaded — edit or paste your own JSON below.
JSON Schema (Optional)
How to Validate JSON Online
Step-by-step guide for using the JSON Validator.
- Paste your JSON string into the Input JSON box above.
- Click Validate JSON — the result appears instantly.
- If valid, you'll see a green success message and JSON statistics.
- If invalid, the error panel shows the exact error type, message, and line number.
- Fix your JSON and validate again until it passes.
Common JSON Errors & Fixes
| Error | Example (Wrong) | Fix |
|---|---|---|
| Trailing comma | {"a":1,} |
{"a":1} |
| Single quotes | {'key':'val'} |
{"key":"val"} |
| Unquoted key | {key: "val"} |
{"key": "val"} |
| Missing comma | {"a":1 "b":2} |
{"a":1,"b":2} |
| Comments | {"a":1} // comment |
Remove comments (JSON doesn't support them) |
Frequently Asked Questions
What does a JSON validator check?
A JSON validator checks whether your JSON follows the correct syntax rules, including quotes, commas, brackets, nesting, and value formatting. This tool also supports JSON Schema validation (Draft 2020-12) — enter a JSON Schema to validate your data structure against custom rules.
Can a JSON validator fix broken JSON automatically?
A validator mainly detects errors; if you also want cleanup or repair, pair it with a JSON Formatter or JSON Repair tool.
Why is valid JavaScript object syntax not valid JSON?
JSON is stricter than JavaScript objects and requires double-quoted keys, double-quoted strings, and no trailing commas. Comments are also not allowed in JSON.
Does my JSON get uploaded to a server?
No. All validation runs entirely in your browser using JavaScript. Your JSON data never leaves your device.
What's the difference between validation and formatting?
Validation checks correctness — is this valid JSON? Formatting also beautifies the JSON with indentation. Use our JSON Formatter if you also want to format your output.
JSON Validator vs JSON Formatter — What's the Difference?
Both tools check your JSON syntax, but they serve different purposes. Understanding the distinction helps you pick the right tool.
| Feature | ✅ JSON Validator (this tool) | 📝 JSON Formatter |
|---|---|---|
| Primary goal | Syntax + JSON Schema validation | Format + validate + minify JSON |
| JSON Schema | ✅ Full support (Draft 2020-12) | ❌ Syntax only |
| Error reporting | Exact error type, message & line | Error panel with position |
| Output | Valid/Invalid status + statistics | Beautified or minified JSON |
| JSON statistics | ✅ Keys, arrays, depth, size | ❌ Not shown |
| Best for | CI checks, syntax validation, quick pass/fail | Debugging, reading, reformatting output |
Real-World Error Scenarios
These are the errors developers hit most often. The validator shows the exact line so you can fix them in seconds.
{
"env": "production",
"debug": false,
}
{
"env": "production",
"debug": false
}
{"msg": "Hello "World""}
{"msg": "Hello \"World\""}
\". Use our JSON Escape tool to do it automatically.{
"items": [1, 2, 3
}
{
"items": [1, 2, 3]
}
[ needs a closing ], and every { needs a closing }. The validator shows you the exact position of the mismatch.When Should You Validate JSON?
Validate request bodies to prevent 400 errors from the server.
Fail builds early when config files like package.json are broken.
Validate exported data before feeding it into a database or service.
Hand-editing JSON is error-prone. Always validate after touching it.
All validation logic runs entirely in JavaScript on your device. There is no server involved — no uploads, no logging, no analytics on your JSON content. Safe for sensitive payloads: API keys, PII, authentication tokens, internal configs.
About This JSON Validator
Validate JSON syntax and structure with detailed error reporting. This tool is part of the AI JSON Tools collection, providing specialized functionality for developers working with JSON data. All processing happens entirely in your browser—your data never leaves your device.
Comprehensive Syntax Validation
This validator goes beyond basic JSON.parse() checking. It implements the complete JSON specification (RFC 8259) with additional practical checks. The validator examines: proper UTF-8 encoding, valid number formats (including scientific notation), correct string escaping, array and object structure, and proper use of whitespace. It also checks for common anti-patterns like duplicate keys (which are technically valid but often indicate bugs) and excessively deep nesting (which can cause stack overflows).
Error Reporting That Actually Helps
When validation fails, you get more than just 'SyntaxError'. The tool provides: exact line and column numbers, surrounding context (10-20 characters before/after the error), suggested fixes based on common mistakes, and links to relevant documentation. For complex errors like missing closing brackets, it shows the entire structure with the problematic section highlighted. The error messages are written for humans, not just developers familiar with parser terminology.
Schema Validation (JSON Schema Draft 2020-12)
Beyond syntax, you can validate JSON against JSON Schema definitions. This is crucial for API development where data must conform to specific structures. The validator supports the full JSON Schema Draft 2020-12 specification, including: required fields, type constraints (string, number, integer, boolean, array, object), pattern matching for strings, minimum/maximum values for numbers, array item validation, object property validation, and conditional logic (if/then/else). You can paste your schema directly or load from a URL.
Integration with Development Workflows
Teams integrate this validator into their CI/CD pipelines using the command-line version (available separately). Before committing code, developers run validation on all JSON configuration files. API teams use it to validate request/response payloads during testing. The tool can output results in multiple formats: human-readable text, JSON for programmatic processing, and JUnit XML for test reporting systems. This ensures JSON quality gates are enforced throughout the development lifecycle.
Privacy & Security Guarantee
No data leaves your browser. All JSON processing happens locally using JavaScript. This means you can safely work with sensitive information like API keys, authentication tokens, customer data, and proprietary configurations. There is no server-side processing—we don't even have servers that could store your data.