A JSON formatter and validator is a free online developer tool that instantly formats raw, unreadable JSON into clean, properly indented, syntax-highlighted output — and simultaneously validates whether your JSON is structurally correct, pinpointing exactly where any errors exist. Paste your JSON, click format, and get a beautifully structured, colour-coded, human-readable result in seconds. If your JSON contains errors, the validator tells you precisely where the problem is and what went wrong.
JSON — JavaScript Object Notation — is the universal data interchange format of the modern web. APIs return it. Configuration files use it. Databases store it. Developers debug it, log it, transform it, and transmit it dozens of times every working day. But raw JSON arriving from an API response is typically compressed into a single unbroken line with no whitespace, no indentation, and no formatting — completely unreadable to the human eye.
Takes compressed, minified, or poorly formatted JSON and outputs a clean, properly indented, human-readable version. Every nested object and array is indented correctly, every key-value pair is on its own line, and the entire document structure becomes immediately visible.
Before formatting:
{"user":{"id":1042,"name":"Sarah Ahmed","email":"sarah@example.com","roles":["admin","editor"],"preferences":{"theme":"dark","notifications":true}}}
After formatting: Clean, indented, colour-coded JSON with all nesting clearly visible.
Parses your JSON against the official JSON specification (RFC 8259) and immediately reports whether it is valid. If errors exist, a good JSON validator online identifies the exact line number and character position of every error.
The reverse of formatting. Takes human-readable, indented JSON and strips out all unnecessary whitespace, line breaks, and indentation to produce the smallest possible valid JSON string — ideal for API payloads and production environments.
The most common JSON error. JSON does not allow a comma after the last item in an object or array — unlike JavaScript, Python, and most modern programming languages.
Invalid: {"name": "Ahmed", "age": 30,}
Valid: {"name": "Ahmed", "age": 30}
JSON requires double quotes for both keys and string values. Single quotes — valid in JavaScript and Python — are strictly invalid in JSON.
Invalid: {'name': 'Ahmed'}
Valid: {"name": "Ahmed"}
JSON object keys must always be strings wrapped in double quotes. JavaScript allows unquoted keys but JSON does not.
Invalid: {name: "Ahmed", age: 30}
Valid: {"name": "Ahmed", "age": 30}
JSON does not support comments of any kind — not // single-line comments and not /* */ block comments.
JSON booleans must be lowercase true and false. JSON null must be lowercase null. Capitalised versions (True, False, Null) are invalid.
Each item in an array and each key-value pair in an object must be separated by a comma — except the last one.
| Character | Must Be Written As |
|---|---|
| Double quote | " |
| Backslash | \ |
| Newline |
|
| Tab | |
| Data Type | Example | Notes |
|---|---|---|
| String | "hello world" | Must use double quotes — single quotes invalid |
| Number | 42, 3.14, -7, 1e10 | Integer or decimal, positive or negative |
| Boolean | true, false | Lowercase only — True/False/TRUE invalid |
| Null | null | Lowercase only — Null/NULL invalid |
| Object | {"key": "value"} | Unordered collection of key-value pairs |
| Array | ["a", "b", "c"] | Ordered list of values |
💡 Privacy Note: The JSON formatter processes all your input entirely within your browser using local JavaScript. Your data is never transmitted to any server — safe for sensitive API payloads, credentials, and internal data.
Yes. This online JSON formatter and validator is 100% free with no account, no subscription, and no payment required. Format, validate, and minify JSON as many times as you need.
No. A privacy-respecting JSON formatter processes all your input entirely within your browser using local JavaScript. Your JSON data is never transmitted to any server, stored, or logged anywhere.
Formatting (pretty printing) transforms valid JSON into a human-readable, indented layout without changing the data. Validation checks whether the JSON is syntactically correct according to the JSON specification — it tells you whether the JSON can be successfully parsed by any standard JSON parser.
JSON does not allow a comma after the last item in an object or array. This is a common mistake because JavaScript, Python, and most modern programming languages allow trailing commas. Simply remove the comma after the final key-value pair in each object and after the final element in each array.
No. The JSON specification explicitly does not support comments of any kind. If you need a JSON-like format that supports comments, consider JSONC (used by VS Code configuration files) or JSON5 — both are supersets of JSON that add comment support.
JSON minification removes all unnecessary whitespace, line breaks, and indentation — producing the smallest possible valid JSON string. Minified JSON is useful for API responses, storage, and transmission where reducing byte count improves performance. The data content is identical to the formatted version.
JSON stands for JavaScript Object Notation. It was created by Douglas Crockford in the early 2000s as a lightweight, human-readable data interchange format based on a subset of JavaScript syntax. Despite the JavaScript in its name, JSON is completely language-independent and is supported natively in virtually every modern programming language.
In VS Code, open a .json file, right-click in the editor, and select Format Document — or use the keyboard shortcut Shift+Alt+F on Windows/Linux or Shift+Option+F on macOS. An online JSON formatter is useful when you are working outside VS Code or need to quickly format a snippet from an API response.
Use our free Free Online JSON Formatter & Validator — no signup, no download, works instantly on any device.
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