JSON Formatter & Validator
Format, validate, minify, and explore JSON instantly — with syntax highlighting, tree view, and error reporting. All in your browser.
string — "hello"
number — 42, 3.14
boolean — true, false
null — null
object — {"key": "value"}
array — [1, 2, 3]
nested — {"a": {"b": 1}}
\" — double quote
\\ — backslash
\n — newline
\t — tab
Trailing commas
Single quotes
Unquoted keys
Comments (not allowed)
RFC 8259 (JSON)
ECMA-404
MIME: application/json
UTF-8 encoding
REST API responses
Configuration files
Data interchange
NoSQL databases
What is JSON?
JSON (JavaScript Object Notation) is a lightweight, text-based data interchange format defined in RFC 8259. It is language-independent but uses conventions familiar to programmers of the C-family of languages. JSON is the dominant format for APIs, configuration files, and data storage in modern web development.
Why Format JSON?
Raw or minified JSON is difficult to read and debug. A JSON formatter adds proper indentation and line breaks, making the structure immediately visible. This is essential when inspecting API responses, debugging configuration issues, or reviewing data exports. Syntax highlighting further improves readability by color-coding keys, strings, numbers, and other value types.
JSON Validation
JSON has strict syntax rules: keys must be double-quoted strings, no trailing commas are allowed, and comments are not part of the specification. Common errors include using single quotes instead of double quotes, adding trailing commas after the last element, and using unquoted property names. A JSON validator catches these errors instantly and reports the exact location.
Beautify vs Minify
Beautify (pretty-print) reformats JSON with consistent indentation (typically 2 spaces) and line breaks, making it easy to read and edit. Minify removes all unnecessary whitespace to produce the smallest possible output. Minified JSON is ideal for API transmission, storage, and production configuration files where readability is not needed.
JSON Syntax Rules
| Rule | Valid Example | Common Error |
|---|---|---|
| Double Quotes Only | {"key": "value"} | Using single quotes {'key': 'value'} |
| Keys Must Be Quoted | {"name": "Gab"} | Missing quotes {name: "Gab"} |
| No Trailing Commas | [1, 2, 3] | Extra comma [1, 2, 3,] |
| Specific Data Types | "string", 123, true, null | Using undefined or functions |
Frequently Asked Questions
What does a JSON formatter do?
A JSON formatter takes raw or minified JSON data and reformats it with proper indentation, line breaks, and syntax highlighting so it's easy to read and debug. It can also validate the JSON structure and report errors with line numbers.
How do I validate JSON online?
Paste your JSON into the input field on this page. The tool instantly parses it and reports whether it's valid. If there are syntax errors, it shows the exact error message and line number so you can quickly find and fix the problem.
What is the difference between JSON minify and beautify?
Beautify (or pretty-print) adds indentation and line breaks to make JSON human-readable. Minify removes all unnecessary whitespace to produce the smallest possible output, which is ideal for network transmission and storage. Both operations preserve the data — only the formatting changes.
Is it safe to paste sensitive JSON data here?
Yes. All formatting and validation happens entirely in your browser using JavaScript. No data is sent to any server. Your JSON never leaves your device, making it safe to use with API responses, configuration files, and other sensitive data.
What is the maximum JSON size this tool supports?
This tool supports JSON input up to 1 MB in size. For most use cases — API responses, configuration files, database exports — this is more than sufficient. The tool shows real-time stats including the size of your JSON data.
Related Tools
- JSONPath Tester — Query and extract data from JSON using JSONPath expressions.
- JWT Decoder — Decode and debug JSON Web Tokens online.
- Regex Tester — Test and debug regular expressions with real-time highlighting.