JSON Formatter
Free Json Formatter for tools. Free online tool with accurate results using verified formulas. Includes worked examples, FAQ, and instant calculations.
Formula
Format: JSON.stringify(JSON.parse(input), null, 2) | Minify: JSON.stringify(JSON.parse(input))
The tool first parses the input to validate JSON syntax, then serializes it either with indentation or as a compact one-line string.
Worked Examples
Example 1: Format an API response
Problem:Make a single-line API response easier to review.
Solution:Input: {"user":{"id":123,"name":"John"},"status":"active"} Formatted output: { "user": { "id": 123, "name": "John" }, "status": "active" }
Result:Nested objects become readable and easier to debug.
Example 2: Catch invalid syntax
Problem:Why is this JSON invalid: {name: "John", "age": 30,}?
Solution:Two issues exist: the key name is unquoted and there is a trailing comma after the last property. Valid JSON must use double-quoted keys and cannot end an object or array with an extra comma.
Result:The formatter surfaces the parse error before you ship broken JSON.
Example 3: Minify for production
Problem:Shrink a formatted configuration object before deployment.
Solution:Pretty JSON keeps the structure readable during editing. Minified JSON removes line breaks and spaces so the same data takes fewer bytes over the network.
Result:Same data, smaller payload.
Frequently Asked Questions
Why format JSON?
Formatted JSON adds indentation and line breaks so you can inspect nested objects, arrays, and keys quickly. It is much easier to debug than a single minified line.
Why minify JSON?
Minified JSON removes unnecessary whitespace to reduce payload size. That makes network transfers and storage more efficient, especially in production environments.
What makes JSON invalid?
Common errors include trailing commas, unquoted keys, single quotes instead of double quotes, missing braces or brackets, and unescaped special characters inside strings.
Can JSON include comments?
Standard JSON does not allow comments. If you need comments in configuration data, use a different format such as YAML or a JSON-compatible extension like JSON5.
Does this formatter send my JSON to a server?
No. The formatter runs in your browser. Your JSON is parsed, formatted, and validated client-side.
What is the difference between JSON and XML?
JSON is more compact, easier to read, and faster to parse than XML. JSON uses key-value pairs and arrays, while XML uses tags and attributes. JSON is the standard for REST APIs, while XML is still used in legacy systems and SOAP services.
How do I validate JSON syntax?
Paste your JSON into a validator to check for common errors like missing commas, unmatched brackets, unquoted keys, trailing commas, and single quotes instead of double quotes. Valid JSON requires double-quoted strings and no trailing commas.
What are common JSON formatting errors?
The most frequent errors are trailing commas after the last item, single quotes instead of double quotes, unquoted property names, comments (JSON does not support comments), missing colons between keys and values, and mismatched brackets or braces.
Can JSON contain comments?
Standard JSON does not support comments. This is by design to keep the format simple and unambiguous. Workarounds include using a _comment key, JSONC (JSON with Comments used by VS Code), or JSON5 which allows comments and other relaxed syntax.
What is JSON Schema?
JSON Schema is a vocabulary for annotating and validating JSON documents. It defines expected structure, data types, required fields, value constraints, and patterns. It is widely used for API documentation, form validation, and configuration file validation.
Background & Theory
JSON is a text-based format for structured data. It supports objects, arrays, strings, numbers, booleans, and null.
Common validation rules
- Keys must be wrapped in double quotes.
- Strings must use double quotes.
- Objects use curly braces and arrays use square brackets.
- Trailing commas are not allowed.
- Comments are not part of standard JSON.
Typical use cases
- API request and response payloads
- Configuration files
- Browser storage and application state
- Data exchange between services
History
JSON emerged from JavaScript object notation in the early 2000s and quickly replaced XML in many browser-to-server workflows because it was much lighter and easier to parse.
Douglas Crockford popularized the format, and JSON was later standardized through ECMA-404 and RFC 8259 so implementations across languages could follow the same grammar.