Free JSON Formatter & Validator
Paste messy JSON, get it pretty-printed, minified, or validated — with plain-English error messages when something is wrong.
How to use the JSON formatter
- Paste your JSON into the input box.
- Click Format to pretty-print it with indentation, Minify to compress it to one line, or Validate to check it without changing anything.
- Copy the result with one click when you are happy.
JSON tips for developers
JSON is strict in ways that trip up even experienced developers. The three errors this validator catches most: trailing commas after the last item in an object or array (legal in JavaScript, illegal in JSON), single quotes around strings (JSON demands double quotes), and unquoted keys. Another classic is pasting JSON that contains comments — handy for humans, fatal for parsers. When debugging an API response, format it first: pretty-printing turns a wall of text into a readable tree where a missing bracket jumps out immediately. Minify when you need to shrink payloads or paste JSON into a URL parameter or a single-line config field. And a privacy note worth repeating: because this tool runs entirely in your browser, API keys and tokens inside your JSON never leave your device — unlike server-side formatters, there is nothing to leak.
Frequently asked questions
What is JSON?
JSON (JavaScript Object Notation) is a lightweight text format for structured data — the lingua franca of web APIs, config files, and data exchange.
What are the most common JSON errors?
Trailing commas, single-quoted strings, unquoted keys, comments, and mismatched brackets or braces. The validator reports the exact position of the problem.
When should I minify JSON?
When size matters: API payloads, embedding JSON in URLs or HTML attributes, or storing it in size-limited fields. For reading and debugging, always use formatted output.
Is my JSON data uploaded anywhere?
No. Parsing and formatting happen locally in your browser. Paste API responses containing secrets with confidence — they never leave your machine.