JSON Validator & Beautifier
100% Free · Client-Side
Validate, beautify, and minify JSON with detailed error messages. Configurable indentation and tree view.
JSON Editor
What is the JSON Validator & Beautifier?
The JSON Validator parses and validates any JSON string, showing exactly where syntax errors occur. It also beautifies (pretty-prints) valid JSON with consistent indentation for readability, or minifies it to reduce payload size. All processing is done locally in your browser.
Common JSON Syntax Errors
| Error | Example |
|---|---|
| Trailing comma | {"a": 1,} |
| Single quotes | {'key': 'value'} |
| Unquoted keys | {key: "value"} |
| Undefined/NaN values | {"a": undefined} |
| Comments in JSON | {"a": 1 // comment} |
Common Use Cases
- Validate API responses before processing them in code
- Debug JSON syntax errors from logs, config files, or API payloads
- Beautify minified JSON from network requests (DevTools) for manual inspection
- Minify JSON configuration files before deploying to reduce file size
- Validate
package.json,tsconfig.json, or other configuration files
Frequently Asked Questions
What's the difference between JSON and JSON5?
JSON is strict — no comments, no trailing commas, all keys must be quoted. JSON5 is a superset that allows these. This tool validates strict JSON (RFC 8259).
Can I validate very large JSON files?
Yes — processing is done locally in the browser without server uploads. Performance depends on your device's memory and the browser's JavaScript engine.