JSON Formatter
Paste messy JSON and get beautifully formatted output instantly.
Runs in your browser - nothing leaves your deviceHow It Works
Paste
Paste your messy JSON into the input panel
Auto-Format
Instantly formatted with syntax highlighting
Copy or Download
Copy to clipboard or download as .json
About the JSON Formatter
JSON that arrives as one unbroken line is hard to read and harder to debug. This JSON Formatter takes that compressed string, checks it is actually valid, and prints it back with proper indentation and color coding for keys, strings, numbers, booleans, and null. If the text is not valid JSON, it tells you what broke instead of silently producing garbage, so you can spot a missing comma or an unquoted key fast.
You paste text into the input panel and formatting happens as you type. The tool runs JSON.parse on your input and, when that succeeds, re-serializes it with your chosen indent width so the structure lines up. Keys show in cyan, strings in purple, numbers in green, booleans in amber, and null in gray. If JSON.parse throws, the output panel shows an Invalid JSON message with the exact parser error, such as the position where an unexpected token was found.
It is free, needs no signup, and the note under the title is literal: everything runs in your browser and nothing is sent to a server. That matters when the JSON is an API response with tokens, a config file, or a database dump you should not paste into a random web service. You can copy the formatted result to your clipboard or download it as a .json file without an account or a network round trip.
How to use the JSON Formatter
- 1Paste or type your JSON into the INPUT panel on the left.
- 2Watch the OUTPUT panel format and color the result the moment your text parses.
- 3Choose 2 spaces or 4 spaces next to the Indent label to set the indentation width.
- 4If you see the Invalid JSON message, read the parser error and fix the spot it points to.
- 5Click Copy to put the formatted text on your clipboard, or Download to save it as formatted.json.
- 6Click Clear to empty the input and start over.
What you can use it for
Reading an API response
A REST endpoint returns one long minified line. Paste it here to see the nested objects and arrays laid out with indentation, so you can trace which field holds the value you need before writing code against it.
Catching a syntax error
Your config file will not load and the app just says parse error. Drop the file contents in and the Invalid JSON message reports the exact position of the trailing comma, missing quote, or stray bracket that broke it.
Cleaning JSON for a commit
You edited a fixture or settings file by hand and the indentation is now inconsistent. Format it at 2 or 4 spaces to match your project style, then download formatted.json or copy it back into your editor.
Sharing a readable payload
You need to send a teammate a request body from a log. Format it so the keys are aligned and color coded, then copy the clean version into your chat instead of pasting an unreadable single line.
Frequently asked questions
Does my JSON get uploaded when I format it?
No. Parsing, formatting, and highlighting all run in your browser with the built-in JSON.parse and JSON.stringify functions. Nothing is sent to a server, which is why you can safely format responses that contain API keys, tokens, or private records. Copy and Download also work entirely on your device.
What indentation widths can I format with?
Two: 2 spaces or 4 spaces, selected with the buttons next to the Indent label. There is no tab or minify option in this tool. Switching the indent width re-formats the current output instantly, so you can compare both widths without re-pasting your input.
Why does it say Invalid JSON?
The formatter only accepts strict JSON that JSON.parse can read. Common causes are trailing commas, single quotes, unquoted keys, comments, or a truncated document. The error line below the message repeats the parser's own description, which usually names the unexpected token or position so you can find it.
Can it handle very large numbers exactly?
Not always. Because it parses into JavaScript numbers, integers larger than 9007199254740991 (Number.MAX_SAFE_INTEGER) can lose precision, and the formatted output will show a rounded value. For IDs or financial amounts that exceed that range, keep them as strings in your source data before formatting.
Does formatting change my data?
It re-serializes the parsed value, so structure and values are preserved, but a few surface details change. Insignificant whitespace is normalized, and JSON.stringify uses its own output form for things like escaped characters. Key order is kept as-is; the tool does not sort or reorder keys.
Is there a size limit on the input?
There is no fixed character cap in the tool. The practical limit is your browser's memory, since the whole document is parsed and re-highlighted on every keystroke. Very large files may feel slow because highlighting runs a regular expression over the entire formatted string as you type.