Just Tool It /
JSON Formatter
On-device — nothing uploaded
JSON Formatter & Validator
Paste JSON. Validate, beautify, or minify it. Errors point straight to the line.
Why format JSON in your browser?
JSON often contains the kind of data you'd rather not paste into a random website — API responses with tokens, config dumps with credentials, exported user records. Server-side formatters see all of it. Just Tool It doesn't: parsing and re-printing happen entirely in this tab using the browser's own JavaScript engine. Close the tab and your JSON is gone.
How to use the JSON Formatter
- Paste your JSON into the input box.
- Pick an indent. 2 spaces is the most common; pick Compact to minify.
- Click Process to beautify, or Validate to check syntax only.
- Copy or download the result. If there's an error, the message points to the line and column.
Frequently asked questions
Is my JSON sent anywhere?
No. Parsing uses the browser's built-in
JSON.parse and the formatted output is generated with
JSON.stringify — both run locally in this tab. Your JSON never leaves the browser. You can
confirm by opening developer tools and watching the Network panel: no requests are made.
What does "Try to repair common mistakes" do?
It tries small, conservative fixes that often come from copy-pasting: removes trailing commas, converts
single quotes to double quotes for keys and string values, strips JavaScript-style
// and
/* */ comments, and unwraps a leading variable = assignment. If your input is
valid JSON already, this option has no effect.
Does it support large JSON files?
Yes — within your device's memory. Because everything runs in the browser, the practical ceiling is your
available RAM, not a server upload limit. Several megabytes of JSON is no problem on modern machines.
How are errors reported?
When the JSON is invalid, the status bar shows the parser's message together with the approximate line and
column. The offending line is highlighted by selecting it inside the input box so you can find it
instantly.