JSON Formatter and Validator — Free, Nothing Uploaded
Turn a wall of JSON into something readable — or back into one line.
Runs on your device What you paste is processed by your own browser. It is never sent to a server, and it is not stored anywhere after you leave the page.
Short answer
JSON can be formatted and validated for free in a web browser without sending it anywhere. The text is parsed with the browser's own JSON parser, which both proves it is valid and reports the exact position of the first syntax error, and is then re-serialised with the chosen indent — two spaces, four spaces or a tab — or with no whitespace at all when minifying. Because the parsing happens locally, an API response full of customer data can be inspected without it leaving the device.
At a glance
| Accepts | Any JSON text |
|---|---|
| Produces | Formatted or minified JSON |
| Processing | In your browser |
| Price | Free, no limits |
| Account | Not required |
Formatting and validating are the same operation here, which is why there is no separate validate button. Nothing can be re-indented without first being parsed, so a document that comes back formatted is a document that parsed — and one that does not is reported with the parser's own message, naming the character position where it gave up.
Sorting keys is off by default, and worth turning on for exactly one job: comparing two documents that should be identical. Two configs that differ only in the order their keys were written produce a diff full of noise; sorting both first reduces it to the lines that genuinely disagree. For anything else, leave the order alone — in a hand-written config, it usually carries meaning.
How to use it
- 1
Paste your JSON
Drop it into the box. An API response, a config file, a log line — anything that should parse as JSON.
- 2
Choose how it should look
Formatted with two spaces suits almost everything. Switch to minified to strip every byte of whitespace.
- 3
Convert
The result appears below. If the JSON is broken, the parser says where instead of producing anything.
- 4
Copy it out
Copy puts it on the clipboard; Download saves it as a .json file.
Frequently asked questions
Is my JSON uploaded anywhere?
No. The browser's own JSON parser does the work inside the page. There is no request carrying your text, which you can confirm in the network panel or by going offline after the page loads.
Can I paste JSON that contains real customer data?
That is exactly what this is for. The text is never transmitted, never written to storage and gone when you close the tab — unlike a formatter that posts your payload to its own server to render the result.
What does minifying actually save?
Every space, tab and newline between tokens. On a heavily indented document that is commonly 20–30% of the bytes, and it changes nothing about what the JSON means — the two forms parse to exactly the same value.
Why does my file fail with a trailing comma?
Because JSON does not allow one, even though JavaScript does. The same goes for comments, single-quoted strings and unquoted keys: those are JavaScript object literals or JSON5, not JSON, and a strict parser rejects them.
Will sorting the keys change my data?
No. Object key order is not part of what a JSON object means, so reordering it produces an equivalent document. Arrays are never touched, because an array's order is its content.