json formatter
JSON Formatter & Validator
Paste your JSON to instantly format, validate, and beautify it with syntax highlighting. Minify for production or expand for readability.
Free Online JSON Formatter & Validator
Our JSON formatter instantly beautifies, validates, and syntax-highlights your JSON data. Paste raw or minified JSON into the input panel and see it transformed into a clean, readable format with color-coded keys, strings, numbers, booleans, and null values. Everything runs in your browser — your data never leaves your device.
The tool supports beautifying with 2-space or 4-space indentation, minifying JSON for production use, and provides detailed statistics including key count, nesting depth, and file size. When your JSON contains syntax errors, the validator pinpoints the exact location and type of error to help you fix it quickly.
What Is JSON?
JSON (JavaScript Object Notation) is a lightweight data interchange format that is easy for humans to read and write, and easy for machines to parse and generate. Despite its name, JSON is language-independent and is used by virtually every modern programming language, API, and web service.
JSON was derived from JavaScript in the early 2000s and standardized as ECMA-404. Today it is the dominant format for transmitting data between a server and a web application. REST APIs, configuration files, databases like MongoDB, and even package managers like npm all use JSON as their primary data format.
JSON Syntax Rules
JSON has a simple but strict syntax. Objects are enclosed in curly braces {} and contain key-value pairs separated by commas. Every key must be a string wrapped in double quotes. Arrays are enclosed in square brackets [] and contain ordered lists of values separated by commas.
JSON supports six data types: strings (in double quotes), numbers (integer or decimal), booleans (true or false), null, objects, and arrays. Notably, JSON does not support comments, trailing commas, single quotes, or undefined values — these are common sources of validation errors.
Common JSON Errors and How to Fix Them
Trailing commas are the most frequent mistake. JSON does not allow a comma after the last item in an object or array. For example, {"a": 1, "b": 2,} is invalid — remove the final comma.
Single quotes instead of double quotes will cause a parse error. JSON requires all strings and keys to use double quotes: {"name": "value"} is valid, but {'name': 'value'} is not.
Unquoted keys are valid in JavaScript objects but not in JSON. Every key must be wrapped in double quotes: {name: "value"} should be {"name": "value"}.
Missing commas between key-value pairs or array items will cause parsing failures. Each pair or element must be separated by a comma, except for the last one.
Beautify vs Minify — When to Use Each
Beautified (pretty-printed) JSON uses indentation and line breaks to make the structure visually clear. This is ideal during development, debugging, code reviews, documentation, and any time a human needs to read and understand the data. Our tool defaults to 2-space indentation, which is the most common convention.
Minified JSON removes all unnecessary whitespace, reducing file size. This is optimal for production environments, API responses, data storage, and network transmission where every byte matters. Minification can reduce JSON size by 20–40% depending on the depth and formatting of the original.
Frequently Asked Questions
Is my JSON data secure when using this tool?
Yes. All processing happens entirely in your browser using JavaScript's built-in JSON.parse() and JSON.stringify() methods. No data is sent to any server, stored in any database, or transmitted over the network.
What's the maximum JSON size this tool can handle?
The tool can handle JSON files up to several megabytes in size, limited only by your browser's memory. For extremely large files (10MB+), you may experience a brief delay during formatting. For files larger than 50MB, a desktop application like VS Code may be more suitable.
Why does my JSON show an error even though it works in JavaScript?
JavaScript is more permissive than the JSON standard. Common issues include single quotes (JSON requires double quotes), trailing commas (not allowed in JSON), unquoted keys, and comments (JSON doesn't support them). Use our tool to identify exactly which part of your data isn't valid JSON.
What do the statistics mean?
Keys is the total number of unique key-value pairs across all objects. Values counts all values including nested ones. Depth indicates the maximum nesting level of your JSON structure. Size shows the byte count of the beautified version, while Minified shows the compressed size.
Can I format JSONL (JSON Lines)?
This tool is designed for standard JSON. JSONL is a different format where each line is a separate JSON object. If you paste JSONL, only the first line will be formatted correctly. For JSONL support, process each line individually.
What's the difference between JSON and XML?
Both are data interchange formats, but JSON is generally more lightweight, easier to read, and faster to parse. XML uses opening and closing tags which add significant overhead. JSON has become the dominant format for web APIs, while XML is still used in enterprise systems, SOAP services, and document formats like DOCX and SVG.