JSON Formatter & Validator
Validate, pretty-print and minify JSON locally in your browser.
Validate, format or minify JSON
Process JSON locally in your browser and get an exact parse error when the input is invalid.
What JSON formatting changes
Pretty-printing changes whitespace and indentation but not the parsed data structure. Minifying removes unnecessary formatting whitespace to make the JSON string more compact.
How to use this tool
- Paste a JSON document into the input field.
- Choose Format for readable two-space indentation or Minify for compact output.
- If parsing fails, use the browser's error message to find the syntax problem.
- Copy the corrected output when valid.
Common JSON syntax mistakes
JSON requires double-quoted property names and string values, does not allow trailing commas, and uses true, false and null as lowercase literals.
Local processing
This version uses the browser's built-in JSON parser. Input is not intentionally sent to a ToolboxKart server by the formatter.
Frequently asked questions
Does formatting change JSON values?
No. It changes whitespace and indentation around the same parsed data structure.
Can JSON use single quotes?
Standard JSON strings and property names use double quotes.
Why is a trailing comma invalid?
The JSON grammar does not permit trailing commas in objects or arrays.
Is my JSON uploaded?
No. Formatting and validation in this release run locally in your browser.