Tool · runs in your browser
Format & validate JSON —
right in your browser.
Pretty-print JSON with 2-space, 4-space, or tab indentation, minify it to one line, and validate as you type — with the exact line and column of any error. Everything runs on your device, so your data never leaves your browser. No signup, no upload, no ads over the editor.
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Frequently asked questions
- Is my JSON uploaded anywhere?
- No. Your JSON is parsed, validated, and formatted entirely in your browser using the built-in JSON engine — nothing is uploaded, stored, or logged. Once the page has loaded it works offline, so it's safe for API responses, config files, tokens, and other confidential data. You can confirm it in your browser's Network tab: no requests go out while you work.
- What is JSON, and what does formatting do?
- JSON (JavaScript Object Notation) is a lightweight text format for structured data — objects with key/value pairs and arrays — used by almost every web API and config file. Formatting (pretty-printing) adds consistent indentation and line breaks so a dense blob becomes readable; minifying strips all that whitespace back out to make the smallest possible payload for shipping over the network.
- What are the most common JSON errors?
- Trailing commas (a comma after the last item in an object or array), single quotes instead of double quotes (JSON requires double quotes on both keys and string values), unquoted keys, comments (JSON doesn't allow // or /* */), and missing commas or brackets. When your JSON is invalid, this tool shows the error message plus the exact line and column so you can jump straight to it.
- Does it validate JSON, and how accurate is it?
- Yes. Validation uses the browser's native JSON parser — the same engine that runs in production JavaScript — so if it validates here, it will parse in your code. There's no custom parser to disagree with the spec. Invalid input shows a clear reason and a pinpointed location rather than a silent failure.
- Is there a size limit, and does it work on mobile?
- There's no server, so there's no per-request cap — the practical limit is your device's memory, and typical API payloads and config files are far below it. Parsing happens on your own machine. The tool runs in any modern browser on Windows, macOS, Linux, Android, and iPhone, with nothing to install.