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JSON Formatter & Validator

Format, beautify and validate JSON with syntax error detection and instant feedback.

About the JSON Formatter

JSON (JavaScript Object Notation) is the most widely used data-interchange format on the web. It powers REST APIs, configuration files, log streams, and data storage across virtually every programming language. Raw JSON returned from an API or log system is often minified (whitespace removed) to save bandwidth, making it very difficult to read. This formatter instantly beautifies it with proper indentation and syntax highlighting.

How to use this tool

  1. Paste your raw or minified JSON into the input area on the left.
  2. The formatter validates and beautifies it automatically as you type.
  3. If the JSON contains errors, the tool highlights the line and character position of the problem.
  4. Copy the formatted output using the copy button, or use the minify option to compact it back.

JSON validation

The formatter validates your input against the JSON specification (RFC 8259). Common mistakes that cause validation failures include:

  • Trailing commas after the last item in an array or object ([1, 2, 3,] is invalid)
  • Single-quoted strings — JSON requires double quotes ('value' should be "value")
  • Unquoted object keys ({name: "value"} should be {"name": "value"})
  • JavaScript comments (// comments are not valid JSON)
  • Undefined or NaN values (JSON only supports strings, numbers, booleans, arrays, objects, and null)

JSON vs JSONC and JSON5

Some tools use extended JSON formats that allow comments or trailing commas (JSONC, JSON5). Standard JSON parsers and APIs do not accept these. If you need to convert YAML to JSON or JSON to YAML, use our YAML to JSON or JSON to YAML converters.

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Frequently asked questions

Does this validate JSON?
Yes. If your JSON is invalid, the tool will show the exact error message and position so you can fix it quickly.
Is my JSON data private?
Yes. All processing happens in your browser. Your JSON is never sent to the server.
What is the maximum JSON size?
The tool handles JSON up to several MB in most browsers. For very large files, performance depends on your device.