JSON Formatter + Validator

Free JSON Formatter & Validator - Format, Minify & Validate JSON Online

Our free JSON Formatter and Validator helps you format, validate, minify, and analyze JSON data instantly. Pretty print JSON for readability, minify for production, validate syntax errors, and get detailed statistics about your JSON structure including depth, object count, array count, and data types. Perfect for developers, API testing, and data analysis.

What is a JSON Formatter and Validator?

A JSON Formatter and Validator is a free online tool that formats, validates, and analyzes JSON (JavaScript Object Notation) data. JSON is the most popular data interchange format used in web APIs, configuration files, databases, and modern applications. Our JSON formatter tool validates JSON syntax to detect errors like missing brackets, extra commas, or invalid data types, formats JSON into pretty-printed human-readable structure with proper indentation, minifies JSON by removing whitespace to reduce file size for production use, and analyzes JSON structure showing depth, object count, array count, and data type statistics. JSON formatting is essential because raw JSON from APIs or databases is often minified in one line making it impossible to read and debug, hand-written JSON frequently contains syntax errors that break applications, and formatted JSON makes code reviews and debugging significantly faster. Our tool serves developers testing APIs and debugging responses, frontend engineers working with JSON configuration files, backend developers validating database exports, data analysts examining JSON datasets, and DevOps engineers reviewing log files and config files in JSON format. The tool processes everything instantly in your browser with no server uploads ensuring your sensitive API data and configurations remain completely private and secure on your machine.

How to Use Our JSON Formatter

Using our free JSON formatter and validator is simple and provides instant comprehensive results.

• Paste or type your JSON data into the input textarea (raw, minified, or pretty-printed)
• Choose your desired output format: Pretty Print for human readability, Minified for smallest file size, or Compact for balanced formatting
• Click 'Format JSON' to instantly validate and format your JSON data
• View validation results - if invalid, see detailed error messages with suggestions for fixes
• Review comprehensive statistics showing JSON depth, object/array counts, data types, and size comparison
• Copy the formatted JSON output with one click using the Copy button
• Download the formatted JSON as a .json file for use in your projects
• Use the Re-validate button to verify the output JSON is still valid after any manual edits

Understanding JSON Format Types

Our tool offers three JSON formatting options to suit different use cases and requirements.

• Pretty Print (Formatted JSON): Adds proper indentation (2 or 4 spaces), line breaks after each property, and human-readable structure. Best for development, debugging, code reviews, documentation, and learning JSON. Increases file size but dramatically improves readability
• Minified (Compressed JSON): Removes all whitespace, line breaks, and unnecessary characters to create the smallest possible file size. Best for production APIs, reducing bandwidth, faster network transfers, and optimizing performance. Cannot be read by humans but perfect for machine consumption
• Compact Format: Balanced approach with minimal whitespace but some structure preserved. Good for logs, configuration files that need occasional manual editing, and situations where you need small file size but occasional readability
• When to use Pretty Print: During development and debugging, for Git commits and code reviews, in documentation and tutorials, when teaching JSON to others
• When to use Minified: For production API responses, in mobile apps to reduce bandwidth, for public APIs serving millions of requests, when every kilobyte matters for performance
• When to use Compact: For log files that humans occasionally review, configuration files that admins might need to edit, situations balancing file size and readability

Common JSON Errors and How to Fix Them

Our validator detects common JSON syntax errors and provides helpful fix suggestions for quick resolution.

• Missing Comma Error: Occurs when comma is missing between object properties or array elements. Fix by adding comma after each property except the last one
• Trailing Comma Error: JSON does not allow comma after the last item in objects or arrays. Remove the trailing comma before closing bracket
• Unquoted Property Names: All object property names must be wrapped in double quotes. Change {name: value} to {"name": value}
• Single Quote Error: JSON only accepts double quotes for strings, not single quotes. Replace all 'text' with "text"
• Mismatched Brackets: Opening brackets must have matching closing brackets. Ensure every { has } and every [ has ]
• Invalid Escape Sequences: Backslashes in strings must escape valid characters. Use \\ for backslash, \n for newline, \t for tab
• Undefined or NaN Values: JSON does not support undefined or NaN. Replace with null or string "NaN"
• Comments Not Allowed: JSON specification does not allow comments. Remove all // and /* */ comment syntax

JSON Statistics and Structure Analysis

Our tool provides detailed statistics helping you understand and optimize your JSON data structure.

• Max Depth: Shows the deepest level of nesting in your JSON. Deep nesting (>5 levels) can impact performance and readability. Consider flattening deeply nested structures for better maintainability
• Object Count: Number of JSON objects (key-value pairs wrapped in {}). High object count may indicate complex data that could benefit from schema validation
• Array Count: Number of arrays (lists wrapped in []). Arrays are efficient for ordered collections but watch for unnecessarily nested arrays
• Total Keys: Count of all property names across all objects. Helps assess data complexity and potential for schema validation or TypeScript interfaces
• Data Type Breakdown: Shows count of strings, numbers, booleans, and null values. Helps identify data composition and potential optimization opportunities
• Size Comparison: Shows input vs output size in bytes and percentage difference. Minifying typically reduces size by 20-40% depending on original formatting
• Line Count: Compares input and output line counts useful for understanding readability vs file size tradeoffs

Pro Tip

Always validate JSON before deploying to production - a single syntax error can break your entire application or API. Use pretty-printed format during development for easier debugging, then minify for production to optimize bandwidth and loading times. When working with APIs, format the response JSON to quickly identify the structure and available data fields rather than trying to read minified API responses. If your JSON has deep nesting (max depth > 5), consider restructuring for better performance and maintainability - deeply nested data is harder to query and slower to parse. Enable your code editor's JSON validation plugin to catch errors as you type rather than discovering them at runtime. For large JSON files (>1MB), use streaming JSON parsers instead of loading everything into memory at once. When debugging API issues, format both your request and response JSON to easily spot differences in structure or unexpected values. Remember that JSON is language-independent but has strict syntax rules - what's valid in JavaScript objects (like unquoted keys or trailing commas) may not be valid JSON.

FAQ

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