Free Online JSON Validator
Validate JSON syntax with detailed error messages, line numbers, and column markers. Format and minify JSON instantly.
data_object Input JSON
code Output Result
Click Validate to check JSON syntax, or Format / Minify to transform JSON.
Key Features
Instant Validation
Validate JSON syntax with detailed error messages, line numbers, and column markers.
Error Detection
Get exact error positions with context lines and a caret (^) marker for quick debugging.
Format & Minify
Beautify JSON with 2-space indentation or compress to a single line with one click.
Privacy Protected
All processing happens locally in your browser. No data ever leaves your device.
Frequently Asked Questions
Getting Started
What is a JSON validator?
The JSON Validator checks whether a given text string conforms to the JSON specification. It parses the input, catches syntax errors like trailing commas, unquoted keys, single quotes, and mismatched brackets, then reports the exact line and column where the parser failed so you can fix the problem immediately.
Is this JSON validator free?
Yes. All tools are completely free and run locally in your browser. No signup, no limits, no hidden costs.
Does the tool store my data?
No. Your JSON data never leaves your browser. All processing happens locally on your device, ensuring complete privacy and security.
Features & Usage
How do I validate JSON?
Simply paste your JSON into the input area and click the "Validate" button. The tool will check syntax automatically and show detailed error information. You can also switch to "Format" to beautify JSON or "Minify" to compress it for production use.
Why does JSON require double quotes?
JSON is a data interchange format, not executable code, and its spec (RFC 8259) mandates double quotes for strings and property names to keep parsing unambiguous across languages. JavaScript object literals are more lenient.
Can this validator handle JSON with comments?
No. Standard JSON does not support comments. Some tools (VS Code settings.json, TypeScript tsconfig.json) use "JSON with comments" (JSONC), which adds // and /* */ comment support as a non-standard extension.
How large a JSON file can I validate?
Most modern browsers handle JSON up to a few megabytes without issue. Around 10 MB you may notice a delay during parsing and syntax highlighting. For typical API payloads (a few kilobytes to a megabyte) the validation is instant.
Troubleshooting
What if my JSON has errors?
The validator will highlight the exact line and position of any syntax errors. Common errors include missing quotes around keys, trailing commas, or unescaped special characters.
Why is my JSON showing as invalid?
Common issues include: unquoted keys (JavaScript objects are not JSON), single quotes instead of double quotes, trailing commas in arrays/objects, and unescaped newlines or tabs in strings.
Can I use this tool offline?
Yes! Once you've visited the page, all functionality works offline thanks to local processing.