JSON Formatter & Validator

JSON (JavaScript Object Notation) is a lightweight data format used to exchange data between applications and APIs. Minified JSON has all whitespace removed for network efficiency, making it unreadable. Formatted JSON adds indentation and line breaks to make it human-readable without changing its meaning. APIs commonly return minified JSON; this tool beautifies it instantly so you can read and debug it.

Yes, completely. All formatting happens in your browser using JavaScript's built-in JSON.parse() and JSON.stringify(). No data is sent to any server. This tool works entirely offline once the page loads — you can disconnect from the internet and it will continue to work. We have no access to or logs of what you paste. Suitable for sensitive API keys, tokens, or internal JSON data.

The most common errors: Trailing commas after the last item in an object or array (not allowed in JSON, but allowed in JavaScript). Single quotes instead of double quotes for strings and keys. Unquoted keys — all keys must be in double quotes. Comments — JSON does not support // single-line or /* block */ comments. Undefined or NaN values — only strings, numbers, booleans, null, arrays, and objects are valid. The validator in this tool will show the exact position of the error.

JSON is a strict text format: all keys must be in "double quotes", and values can only be strings, numbers, booleans, null, arrays, or objects. JavaScript objects are more flexible: they allow unquoted keys, single quotes, trailing commas, functions as values, and comments. JSON is a strict data-interchange subset of JavaScript object syntax. This is why JSON.parse('{"key": undefined}') throws an error — undefined is a JavaScript concept, not a JSON value.

In JavaScript: wrap JSON.parse(str) in a try-catch block. If it throws, the JSON is invalid; the error message will indicate the position. In Python: use json.loads(str) inside a try-except json.JSONDecodeError block. In Java: use ObjectMapper.readTree(str) from Jackson, wrapped in a try-catch. In Go: json.Valid([]byte(str)) returns a boolean. In Bash: echo "$json" | python3 -m json.tool validates and pretty-prints in one command.

Minifying JSON removes all non-essential whitespace (spaces, tabs, newlines) to produce the most compact valid JSON string. Use minification when sending JSON over a network (API responses, webhooks) to reduce payload size and improve performance. A large JSON object can be 30–50% smaller when minified. In development, use formatted JSON for readability. In production API responses, minify automatically — frameworks like Express.js and FastAPI do this by default. Use the Minify button above to compact your JSON for network use.

This tool processes JSON entirely in your browser's JavaScript engine. In practice, it handles up to several megabytes of JSON without issues on modern browsers. Very large JSON files (10MB+) may cause a brief pause during formatting but will complete successfully. For JSON files over 50MB, consider using a command-line tool: python3 -m json.tool large.json or jq . large.json for faster processing. The browser textarea may scroll slowly with very large outputs, but the formatting itself is not size-limited.

JSON5 is a superset of JSON that adds JavaScript-like features: unquoted keys, single quotes, trailing commas, comments, and multi-line strings. It was created to make configuration files more human-friendly. JSON5 files use the .json5 extension. This formatter uses the standard JSON.parse() which does not support JSON5 syntax. If you have JSON5 input with trailing commas or comments, remove them first. Tools like Babel and esbuild internally use JSON5 for config files. True JSON validation uses strict JSON syntax only.

Use the Sort Keys button above. Sorting keys alphabetically makes it easier to scan large JSON objects, compare two JSON responses side-by-side, or produce deterministic output for testing. The sort is applied recursively — all nested objects are also sorted. Note that JSON technically does not guarantee key order (objects are unordered), but in practice most parsers preserve insertion order. Sorted JSON is functionally identical to unsorted JSON — any valid parser will produce the same data regardless of key order.

All three produce valid, functionally identical JSON — the difference is visual style. 2-space indentation is the most compact and common in web APIs and JavaScript projects (the default in Node.js JSON.stringify when using null, 2). 4-space indentation is the Python convention (used by json.dumps(indent=4)) and produces more spacious, readable output. Tab indentation is preferred by some editors (Vim, older conventions) and allows users to configure tab width visually. Select the style that matches your project's code style guide. This formatter defaults to 2 spaces.