JSON Formatter and Validator — Free Online Tool
JSON is the standard data format for APIs, configuration files, and data storage. But raw JSON from APIs is usually minified — a single unreadable line. The JSON Formatter makes it human-readable, validates its structure, and helps you navigate complex nested data.
How to Use the JSON Formatter
- Open the FlipMyCase JSON Formatter.
- Paste your JSON.
- The tool instantly formats, validates, and syntax-highlights it.
- Use the tree view to navigate nested structures.
- Copy the formatted or minified output.
Features
Pretty Print
Converts compact JSON into readable, indented format. Choose 2-space or 4-space indentation.
Validation
Real-time error detection with exact line and character position. Common errors it catches:
- Missing or extra commas
- Unquoted keys
- Single quotes instead of double quotes
- Trailing commas
- Invalid escape sequences
Minify
Removes all whitespace to produce the smallest possible JSON. Useful for reducing payload size before sending to an API.
Tree View
Navigate complex JSON visually. Collapse and expand nested objects and arrays. Click any value to copy its JSON path.
Common JSON Errors and How to Fix Them
Trailing Commas
{"name": "Alice", "age": 30,} ← invalid
{"name": "Alice", "age": 30} ← valid
Single Quotes
{'name': 'Alice'} ← invalid
{"name": "Alice"} ← valid
Unquoted Keys
{name: "Alice"} ← invalid
{"name": "Alice"} ← valid
Comments
{"name": "Alice" /* user name */} ← invalid
{"name": "Alice"} ← valid
JSON does not support comments. Use JSONC or JSON5 if you need them.
JSON in Development Workflows
- API debugging: Format API responses to understand the data structure
- Config files: Validate package.json, tsconfig.json, and other config files
- Database queries: Format MongoDB queries and Elasticsearch mappings
- Testing: Compare expected vs actual JSON responses using the Text Diff tool
- Documentation: Pretty-print JSON examples for API documentation