JSON Formatter & Validator

Paste minified or broken JSON on the left. Instantly see the formatted, validated result on the right.

🔒100% Client-Side. Your JSON is processed entirely in your browser's local memory and is never sent to any server.
Formatted output
Formatted output will appear here

Why use a client-side JSON formatter?

Many online JSON formatters send your input to a backend server for processing. If you're working with production API responses, database exports, or payloads containing customer PII, that's a serious data privacy risk. This tool runs entirely in your browser using JavaScript's native JSON.parse() and JSON.stringify() — no network request is ever made.

Pretty-print JSON in Python

import json raw = '{"name":"Ada","fields":["math","cs"],"active":true}' parsed = json.loads(raw) # Pretty print to console print(json.dumps(parsed, indent=2, ensure_ascii=False)) # Minify minified = json.dumps(parsed, separators=(',', ':')) # Pretty print to file with open('output.json', 'w') as f: json.dump(parsed, f, indent=2, ensure_ascii=False)

Pretty-print JSON in JavaScript / Node.js

const raw = '{"name":"Ada","fields":["math","cs"],"active":true}'; // Parse and validate const parsed = JSON.parse(raw); // throws SyntaxError if invalid // Beautify const pretty = JSON.stringify(parsed, null, 2); // Minify const minified = JSON.stringify(parsed); // Node.js: write to file const fs = require('fs'); fs.writeFileSync('output.json', pretty, 'utf8');

Common JSON validation errors

Trailing commas — JSON does not allow a comma after the last element in an object or array (unlike JavaScript objects). Single quotes — JSON requires double quotes for strings and keys.Undefined / NaN / Infinity — these JavaScript values are not valid JSON.Comments — JSON does not support // comments or /* block comments */.

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