JSON Formatter & Validator
Format, validate, and beautify JSON data with syntax highlighting. Minify or pretty-print with one click.
How to Use the JSON Formatter
- Paste your JSON data into the input editor.
- The tool automatically validates the JSON and highlights any syntax errors.
- Click Format to pretty-print with proper indentation, or Minify to compress.
- Copy the formatted output for use in your code, API calls, or configuration files.
What is JSON and Why Format It?
JSON (JavaScript Object Notation) is a lightweight, text-based data interchange format defined by RFC 8259. It is the dominant format for API communication, configuration files, and data storage in modern web development. JSON supports six data types: strings, numbers, booleans, null, arrays, and objects. Its simplicity and language-independent design have made it the de facto standard for data exchange on the web. Formatting and validating JSON is essential during development and debugging. Minified JSON from API responses or log files is extremely difficult to read without proper indentation. This tool pretty-prints JSON with consistent indentation, making nested structures clear and easy to navigate. It also validates the JSON structure, catching common errors like trailing commas, missing quotes, single quotes instead of double quotes, and unescaped special characters. In security contexts, JSON parsing inconsistencies between different libraries have led to vulnerabilities. Duplicate keys may be handled differently across implementations, enabling parameter pollution. Excessively nested JSON can cause denial-of-service through stack overflow. When testing APIs, always validate both the structure and content of JSON payloads, and be aware that different JSON parsers may interpret edge cases differently.
Frequently Asked Questions
The most common errors include trailing commas after the last element, using single quotes instead of double quotes, unquoted property names, comments (JSON does not support comments), and missing closing brackets or braces. JavaScript object syntax is more permissive than JSON, so code-valid objects may not be valid JSON.
JSON is a strict subset of JavaScript object syntax. JSON requires double-quoted property names and string values, does not allow trailing commas, functions, undefined, or comments. A JavaScript object literal can use single quotes, unquoted keys, and include functions. Use JSON.stringify() to convert a JavaScript object to valid JSON.
JSON is more widely supported and has unambiguous parsing rules, making it safer for machine-to-machine communication. YAML is more human-readable and supports comments, making it popular for configuration. However, YAML's complexity has led to parsing vulnerabilities and surprising type coercions (e.g., 'no' becoming a boolean). Choose based on your use case and risk tolerance.