JSON Formatter & Validator - Format and Validate JSON Online
Ideal when API responses are compressed into a single unreadable line, when inspecting complex JSON structures from backend logs, or when verifying syntax errors in configuration files (config.json) before deployment. It is also widely used for quick debugging of raw responses captured from Postman or curl.
When to Use This Tool
- API Response Readability: Indents minified one-line responses for instant visual comprehension of payloads.
- Server Log Parsing: Quickly parse and inspect raw JSON event records copied directly from loggers like CloudWatch or Datadog.
- config.json Validation: Detect missing commas, unclosed brackets, or syntax typos before deploying configs.
- Postman & curl Debugging: Test and verify payload bodies, error responses, and nested attributes seamlessly.
How to Use
- Input JSON: Paste your unformatted JSON text into the left input editor.
- Apply Formatting: Click the "Format" button to automatically apply indentation and line breaks.
- Syntax Validation: If there are syntax errors, the exact line and position of the issue are displayed.
- Copy & Export: Copy the beautified result to your clipboard or download it as a .json file.
Input & Output Example
Input:
{"user":{"id":1,"name":"Kim","roles":["admin","editor"],"active":true}}
Output:
{
"user": {
"id": 1,
"name": "Kim",
"roles": [
"admin",
"editor"
],
"active": true
}
}
Frequently Asked Questions (FAQ)
Q. Can it handle deeply nested JSON?
A. Yes. Even if arrays and objects are nested across multiple hierarchy levels, appropriate indentation is applied at each depth.
Q. What happens if there are syntax errors?
A. Common syntax mistakes such as missing commas or unquoted keys will be pointed out with exact error line indicators. Since formatting requires valid syntax, you will need to fix these issues first.
Q. Can it process large files?
A. Because processing is executed directly in your browser memory, multi-megabyte JSON files are handled smoothly. Very large files exceeding tens of megabytes may vary in speed depending on your device performance.
Engineering & Privacy Notes
- This tool operates 100% client-side in your browser; your input data is never sent to any remote server.
- Non-standard JSON extensions like JSON5 or JSONC (JSON with comments) are not supported; it strictly parses standard RFC 8259 JSON.
Related Developer Tools
- JSON Schema Generator: Generate standard JSON Schema draft specifications from raw JSON payloads.
- JSON to TypeScript: Convert raw JSON structures into type-safe TypeScript interfaces and types.
- JWT Decoder: Securely inspect Header and Payload JSON claims inside JSON Web Tokens.
- Diff Checker: Compare two JSON files or text snippets side-by-side to highlight exact differences.