JSON Formatter & Validator

How to format and validate JSON online

A compact API response is efficient to send but difficult to read. This free JSON formatter turns it into an indented document you can inspect, without changing string contents or rewriting number tokens.

1. Add your JSON. Paste text, use the clipboard button, open a local file, or drop one onto the input panel. The Examples menu includes valid data and a deliberately broken document.
2. Choose the result. Format JSON produces readable output. Validate checks syntax without replacing the input. Minify removes whitespace between tokens.
3. Inspect errors and warnings. A syntax error prevents output. Duplicate keys and number-range concerns produce warnings while valid syntax remains usable.
4. Explore or export. Switch to Tree, extract a specific property path, copy the output, or download the complete result.

Documents up to 1 MiB validate and format after a short typing pause. For larger inputs, use an action button. Keeping the parser in a worker lets the page handle editing separately from parsing.

JSON formatter, validator, beautifier, or minifier?

These names describe related jobs. A JSON beautifier or pretty printer adds layout. A JSON validator checks grammar. A JSON minifier removes insignificant whitespace. A JSON viewer makes the structure easier to navigate.

Formatting is not an application-level correctness check. A response can be valid JSON while missing a required field or using the wrong type. Use your API’s contract or a separate JSON Schema validator for those rules.

A quick JSON syntax checklist

If a document fails validation, check its boundaries and separators before changing values. Object members use a quoted key, a colon, and a value. Arrays contain ordered values separated by commas. Every opened brace or bracket needs a matching close.

• Use double quotes for object keys and strings.
• Keep commas between members or items, with none after the final one.
• Use lowercase true, false, and null.
• Escape quotation marks and backslashes inside strings.
• Do not include comments, functions, undefined, NaN, or Infinity in standard JSON.

JSON supports seven root value forms: an object, array, string, number, either boolean literal, or null. In day-to-day API work you will most often receive an object or array.

Common JSON errors and their fixes

A line-and-column pointer shows where the parser could no longer continue. If that character looks correct, check the preceding value, quotation mark, or comma. For a longer walkthrough, read common JSON syntax errors and how to fix them.

A JSON example with nested data

This example combines an object, array, string, number, boolean, and null. In Tree view, expand student to see its fields. Use $.student.name to extract the student’s name or $.skills[1] to select the second skill. The names are fictional sample data.

{
  "student": {
    "name": "Ada",
    "active": true
  },
  "skills": ["HTML", "CSS", "JavaScript"],
  "projects": 3,
  "mentor": null
}

Objects associate property names with values. Arrays preserve order and use indexes starting at zero. The string "3" and the number 3 have different types even though they may look similar on a screen. Explore more in the JSON examples guide.

Large numbers and duplicate keys deserve attention

Many formatters convert a document into ordinary JavaScript values before printing it. That can change an ID beyond the safe integer range, remove repeated object keys, normalize 10.50 to 10.5, or rewrite exponential notation.

This formatter retains the original tokens instead. The numbers 9007199254740993, 10.50, and 1E2 keep their spelling. Repeated keys remain visible and receive a warning. Keeping them visible helps you correct the source rather than overlooking a field that has already disappeared.

Token preservation does not make those values safe in every consuming application. If a receiving system reads a long identifier as a JavaScript number, define a string-based ID in the API contract or use a parser that supports the required precision. The tool highlights the concern without silently altering the document.

JSON formatter and validator: frequently asked questions