JSON Formatter & Validator

What is JSON Formatter & Validator?

JSON (JavaScript Object Notation) is the most common data interchange format — API debugging, config files and log analysis all rely on it. But API responses are often compressed into one unreadable line, and hand-written JSON easily fails to parse because of trailing commas or single quotes. This tool formats, beautifies and validates JSON in one click: when parsing fails it points out the exact line and column with a readable reason (such as "keys must use double quotes"), and the formatted result appears as a collapsible tree so deeply nested structures stay easy to explore. All parsing happens locally in your browser — your data is never uploaded to any server, so it is safe to paste API payloads containing sensitive information.

How to Use

1. Paste JSON into the input area on the left (or drop a .json file, or click "Sample" to load demo data)
2. The tool formats in real time and shows the result on the right; syntax errors are highlighted inline with a readable explanation
3. Use the toolbar to switch indentation (2/4 spaces), copy the result, or download it as a .json file
4. Press Ctrl+Enter to trigger formatting manually

FAQ

Why does {"name":"json"} parse but {name:'json'} does not?

The JSON standard requires keys and strings to use double quotes. In {name:'json'} the key has no quotes and the value uses single quotes — both are invalid. Fix it to {"name":"json"}.

Does JSON support comments or trailing commas?

Standard JSON supports neither // or /* */ comments nor a comma after the last element. Use JSON5 or JSONC if you need comments — this site also offers a JSON5 parser.

Does formatting change my data?

No. Formatting only adjusts whitespace and indentation; keys, values and their order stay unchanged.

Will large files freeze the page?

Inputs over 1MB are automatically processed in a background Web Worker thread so the page stays responsive; all computation happens locally.

Is my JSON uploaded anywhere?

No. All parsing and formatting runs locally in your browser — no network request ever carries your data.

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