JSON Formatter Online — Free & Private
Paste JSON and format it instantly. Validate, beautify or minify — all in your browser with nothing sent to any server.
Format & Minify
One click to beautify messy JSON or minify it to the smallest size.
No Upload
JSON.parse runs in your browser tab. Nothing is ever sent over the network.
Instant Validation
Syntax errors are caught immediately with the exact line and column number.
Input
Output
When you need a JSON formatter
- API debugging — API responses arrive as minified JSON. Format them to read the structure clearly.
- Config files —
package.json,tsconfig.jsonand similar files should be well-formatted for readability. - Log files — Structured logging in JSON format is compact by default. Format entries to debug them.
- Data validation — Catch syntax errors in JSON before shipping it to a database or API.
- Minification before deployment — Reduce JSON payload size in API responses and embedded data.
Frequently asked questions
What is a JSON formatter?
A JSON formatter (also called a JSON beautifier or JSON prettifier) takes compact or minified JSON text and adds proper indentation and line breaks to make it human-readable. It transforms {"name":"John","age":30} into a neatly indented multi-line format.
Is my JSON data sent to a server?
No. This tool runs entirely in your browser using JavaScript's built-in JSON.parse() and JSON.stringify() functions. Your data never leaves your device. There are no servers involved.
What's the difference between formatting and minifying JSON?
Formatting (beautifying) adds whitespace, indentation, and line breaks to make JSON readable by humans. Minifying removes all unnecessary whitespace to produce the smallest possible JSON string — useful for reducing payload sizes in APIs and web apps.
Why is my JSON invalid?
Common JSON errors include: trailing commas (not allowed in JSON), single quotes instead of double quotes for strings, unquoted property names, comments (JSON does not support comments), and missing commas between elements. The error message shows the exact position of the problem.
What indentation size should I use?
2 spaces is the most common convention in JavaScript and Node.js projects. 4 spaces is common in Python and Java. Use whatever matches your project's code style.
Can I format very large JSON files?
Yes, up to the limit of your browser's available memory. For very large files (50MB+), processing may take a few seconds. There are no server-side size limits since everything runs locally.