JSON Formatter & Validator — free, in your browser

Paste any JSON and clean it up in a single click. This formatter pretty-prints messy or minified JSON into a readable, indented structure, and can just as easily collapse it back into a compact single line for production.

Everything runs locally in your browser using the native JSON engine — your data is never sent to a server. That makes it safe for API responses, config files and anything else you would rather not paste into an unknown website.

How it works

When you paste text, the tool hands it to the browser's built-in JSON.parse to turn it into an in-memory object. If parsing succeeds, JSON.stringify rebuilds the text: passing your chosen indent (2 spaces, 4 spaces or a tab) produces the pretty-printed view, while passing no indent produces the minified single line. Validation is simply parsing without re-printing.

Because both JSON.parse and JSON.stringify are native browser functions, no library is downloaded and no request is made to a server. Your JSON stays in the page's memory and is discarded when you close the tab. That local-only design is what keeps API responses, tokens and config files private — nothing is ever uploaded.

When parsing fails, the browser throws a SyntaxError describing what went wrong. The tool surfaces that message so you can jump to the offending character instead of guessing.

When to use it

Reach for Format when you receive a minified API response or a log line and need to actually read the structure. Indenting it reveals the nesting, making it easy to confirm a field exists or trace why a value is missing.

Reach for Minify before storing or sending JSON: configuration embedded in a URL, a payload going over the wire, or a value saved to a database column all benefit from dropping the whitespace. The output is byte-for-byte equivalent data in fewer characters.

Use Validate any time you have hand-edited JSON — a settings file, a fixture, a webhook sample — and want to be sure it will parse before you ship it. Catching a stray comma here is faster than debugging a failed request later.

Tips

Most invalid JSON comes from a handful of mistakes. Trailing commas after the last item in an array or object are valid JavaScript but illegal JSON, so remove them. Strings and keys must use double quotes, never single quotes, and every key must be quoted. Comments are not allowed at all.

If you copied a value from JavaScript source, watch for undefined, NaN or function values — none are valid JSON; use null instead. When the error mentions an unexpected token at a position, count to that character: the real problem is often just before it, such as a missing closing bracket. Run the cleaned text through Format once more to confirm it round-trips.

How to use JSON Formatter

1. Paste or type your JSON into the input box.
2. Choose your preferred indent size: 2 spaces, 4 spaces or a tab.
3. Click “Format” to beautify it, or “Minify” to compact it onto one line.
4. If the JSON is invalid, read the error message to find and fix the problem.
5. Copy the formatted result to your clipboard with one click.

Frequently asked questions

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