DevFmt/

JSON Formatter

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Output

How to use JSON Formatter

JSON Formatter is a free online tool that beautifies and validates JSON data instantly in your browser. Paste raw, minified, or compact JSON and get perfectly indented output with your choice of 2 spaces, 4 spaces, or tab indentation.

The formatter validates your JSON in real-time. If your input contains syntax errors — missing commas, unmatched brackets, or invalid escape sequences — you'll see the exact error message in the status bar so you can fix problems fast.

Key features: configurable indentation, real-time syntax validation, file upload support (.json files), one-click copy and download, line numbers, and byte-size comparison between input and output.

All processing happens client-side in your browser. Your data is never sent to any server, making this tool safe for sensitive configuration files, API responses, and production data. DevFmt is built for developers who need a fast, private JSON formatting tool without signup walls or ads blocking the interface.

FAQ

How do I format JSON online?
Paste your raw or minified JSON into the input panel. DevFmt instantly formats it with syntax validation, configurable indentation (2 spaces, 4 spaces, or tabs), and line numbers. No signup required.
Does this tool validate JSON?
Yes. If your JSON has syntax errors, the status bar shows the exact error message with position information so you can fix the issue quickly.
Is my JSON data sent to a server?
No. All formatting happens entirely in your browser using JavaScript. Your data never leaves your machine — we don't send, store, or log any input.
Can I format large JSON files?
Yes. The formatter handles files of several megabytes directly in the browser. For very large files, use the file upload button instead of pasting.

Related tools

/json/minifier/json/to-csv/json/to-yaml

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