JSON Formatter & Validator
Beautify, minify, and validate JSON instantly in your browser. Syntax error highlighting with precise line and column numbers. No data leaves your machine.
// how to use
Format and validate any JSON in four quick steps.
Paste JSON
Paste your raw JSON into the input box, or click Sample JSON to load a realistic example object.
Choose mode & format
Select Beautify, Minify, or Validate Only, pick your indent size, then click Format.
Fix any errors
If invalid, the output shows the error message with line and column so you can pinpoint the exact problem.
Copy result
Click Copy in the output footer to place the formatted JSON on your clipboard, ready to paste.
What is JSON?
JSON (JavaScript Object Notation) is a lightweight, text-based data interchange format standardised in RFC 8259. It represents data as key-value pairs (objects) and ordered lists (arrays) using a syntax that is both human-readable and trivially machine-parseable. Every modern programming language ships a JSON library in its standard library.
Where is JSON used? Virtually everywhere data moves between systems: REST APIs return JSON responses, configuration files (package.json, tsconfig.json) use JSON, databases like MongoDB and PostgreSQL store JSON natively, and browser localStorage serialises values as JSON strings. If data crosses a network boundary, it is almost certainly JSON.
JSON vs XML. XML was the dominant data format in the early 2000s but has been displaced by JSON in most applications. JSON is smaller (no closing tags), easier to parse, and maps directly to the data structures programmers already use. XML retains advantages in document-centric scenarios (XSLT, schemas, mixed content) and some enterprise integrations.
Common JSON errors. The top mistakes that break JSON are: trailing commas after the last element of an array or object ([1, 2, 3,] is invalid); single-quoted strings — JSON demands double quotes; unquoted object keys — every key must be a double-quoted string; and using JavaScript-only values like undefined, NaN, Infinity, or Date objects, which have no JSON representation.
// faq
What is JSON?
JSON (JavaScript Object Notation) is a lightweight, text-based data interchange format. It represents data using two universal structures: objects (unordered collections of key-value pairs wrapped in {}) and arrays (ordered lists wrapped in []). Values can be strings, numbers, booleans, null, objects, or arrays — no functions, no comments. It was formalised in RFC 8259 and is now the dominant format for APIs and configuration files.
What is the difference between JSON beautify and minify?
Beautifying (also called pretty-printing or formatting) adds newlines and consistent indentation to make JSON easy to read at a glance — ideal during development and debugging. Minifying strips every unnecessary whitespace character, shrinking file size and reducing bytes over the wire. A 10 KB pretty-printed response might be 4 KB minified. Use beautified JSON while developing; ship minified JSON in production APIs where every byte counts.
Why is my JSON invalid? Common mistakes.
The most common culprits are:
1. Trailing commas — {"a":1,} is invalid. Remove the comma after the last item.
2. Single-quoted strings — JSON requires "double quotes" everywhere. 'single quotes' are a JavaScript-only syntax.
3. Unquoted keys — {name: "Alice"} is invalid; it must be {"name": "Alice"}.
4. Comments — JSON has no comment syntax. Strip // ... and /* ... */ before parsing.
5. Non-standard values — undefined, NaN, Infinity, and Date objects are not valid JSON.
What is the difference between JSON and JavaScript objects?
JSON is a text format that looks like JavaScript object literal syntax but is far stricter. JavaScript objects are live, in-memory data structures. The differences:
• JSON keys must be double-quoted strings. JS object keys can be unquoted identifiers.
• JSON values must be one of: string, number, boolean, null, object, array. JS objects can hold functions, undefined, Date, RegExp, symbols, and more.
• JSON does not support trailing commas or comments. Modern JS does (in certain contexts).
• A JS object is never JSON until you call JSON.stringify() on it.
How do I validate JSON in my code?
The universal pattern is to attempt parsing inside a try/catch:
JavaScript: try { const obj = JSON.parse(str); } catch (e) { console.error('Invalid JSON:', e.message); }
Python: import json; try: obj = json.loads(s) except json.JSONDecodeError as e: print(e)
Go: var v interface{}; if err := json.Unmarshal([]byte(s), &v); err != nil { /* invalid */ }
For production APIs, use a schema validator (Ajv for JS, Pydantic for Python, go-playground/validator for Go) to validate structure as well as syntax.
Is my JSON data safe here?
Completely safe. This tool uses only the browser's built-in JSON.parse() and JSON.stringify() functions. No network requests are made, no data is logged, and nothing persists after you close the tab. You can safely paste API keys, auth tokens, private configuration, and any sensitive payload. Check the browser's Network tab in DevTools — you will see zero outbound requests while using the formatter.
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