JSON Formatter & Validator — Format, Validate & Beautify JSON
Format, validate, and beautify JSON data instantly. Paste messy JSON and get clean, indented output with syntax validation and error highlighting.
JSON Formatter
Results update instantly as you type
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The Formula
The JSON formatter works by parsing the raw input string into a JavaScript object using JSON.parse(), which also validates the syntax. Then JSON.stringify() converts the object back to a formatted JSON string with the chosen indentation level (2 spaces, 4 spaces, or tabs). This round-trip process ensures the output is always valid, properly indented, and easy to read.
Variable Definitions
JSON Parser
Parses a JSON string into a JavaScript object. Throws a SyntaxError if the input is not valid JSON.
JSON Serializer
Converts a JavaScript object back to a formatted JSON string with optional indentation and replacer functions.
Indentation Level
The number of spaces or tab character used per indentation level in the formatted output.
JSON Syntax Error
An error thrown when the input contains invalid JSON syntax, such as trailing commas, unquoted keys, or mismatched brackets.
How to Use This Calculator
- 1
Paste or type your raw JSON string into the input field.
- 2
Select your preferred indentation size (2 spaces, 4 spaces, or tab).
- 3
The formatted JSON and character/line counts update instantly as you type.
- 4
If the JSON is invalid, the error message will highlight exactly what went wrong.
Quick Reference
| From | To |
|---|---|
| Valid JSON keys | Must be double-quoted strings |
| Trailing commas | Not allowed in JSON |
| Comments | Not supported in standard JSON |
Common Applications
- Prettifying minified JSON from API responses for debugging.
- Validating JSON configuration files before deployment.
- Formatting JSON data for code reviews and documentation.
- Cleaning up JSON output from database exports and log files.
JSON formatting pipeline — parse, validate, then pretty-print with indentation
Understanding the Concept
JSON (JavaScript Object Notation) is a lightweight data interchange format that has become the standard for API communication, configuration files, and data storage. The JSON Formatter and Validator tool parses raw JSON strings and reformats them with proper indentation, making complex nested structures readable. JSON.parse() is strict: it requires double-quoted strings, no trailing commas, and no comments. When the parser encounters invalid syntax, it throws a SyntaxError with a message indicating the position of the problem. The formatted output uses JSON.stringify() with the specified indentation, which produces clean, human-readable output. Character count helps estimate payload sizes, and line count shows the vertical space the formatted JSON occupies. This tool is essential for any developer working with APIs, configuration management, or data serialization.
Frequently Asked Questions
Sources & References
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