JSON Formatter & Validator

Format JSON

Format parses valid JSON and writes a readable result with fixed two-space indentation. It accepts any valid top-level JSON value. Empty input shows Enter JSON to format.; invalid input begins Invalid JSON: followed by native parser detail. Format alone populates the output; Copy copies only that formatted output, and Clear resets the tool.

Validate JSON

Validate checks syntax only, does not populate formatted output, and reports JSON is valid. for valid input. Empty input shows Enter JSON to validate.; invalid input uses the same Invalid JSON: prefix. The exact error detail varies by browser and may differ from examples you see here.

Compact-to-formatted example

Input: {"name":"Ada","active":true}

Output:

{
  "name": "Ada",
  "active": true
}

This tool always uses two-space indentation, which is fixed and not configurable.

Accepted JSON value types

Object, array, string, number, boolean, and null. Any one of these can be the complete top-level value—not only an object or array.

Strict JSON syntax rules

Strings use double quotes, object property names must be quoted, braces/brackets must balance, and JSON permits neither comments nor trailing commas.

Common JSON errors

Single-quoted strings or names, unquoted property names, comments, trailing commas, and unmatched braces/brackets cause validation failure. Error messages start with Invalid JSON: followed by browser-specific parser detail that varies.

Duplicate object names

Object property names should be unique. If a name occurs more than once in the same object, parsing keeps the later value, so formatting can discard the earlier value.

Browser-dependent limits

The tool has no promised input-size ceiling, but parsing and formatting consume browser memory, so very large pasted inputs may be slow or fail depending on the browser and device.