JSON Formatter & Validator
Pretty-print, validate and minify JSON instantly with clear error locations.
Runs in your browser — your code and data never leave this device
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How to use the JSON Formatter & Validator
- Paste your JSON into the Input box on the left, or click Sample to load a demo object.
- Choose your indent style (2 spaces, 4 spaces, or Tab) from the dropdown.
- Click Format to pretty-print, Minify to compress, or Validate only to check for errors without changing the output.
- Review any error message with its line and column, fix the input, then click Copy output to use the result.
Frequently asked questions
Is my JSON data uploaded to a server?
No. This tool runs entirely in your browser using JavaScript. Your code and data are never uploaded, stored, or sent anywhere — everything stays on this device.
What does Validate only do?
Validate only checks whether your input is valid JSON without reformatting it. If valid, it shows the character count, the top-level type (object, array, string, number, boolean, or null), and for objects or arrays, how many keys or items it contains.
How are error line and column numbers found?
When the browser reports a position (for example “position 42”), the tool counts the characters before that point in your input to calculate the exact line and column, so you can jump straight to the problem.
What is the difference between Format and Minify?
Format adds line breaks and indentation to make JSON readable. Minify removes all unnecessary whitespace to produce the smallest possible single-line output, which is useful for APIs and config files.
Does this tool support large JSON files?
Yes, for typical API responses and config files. Very large inputs (several megabytes) may format more slowly because all processing happens locally in your browser tab.