Format and validate JSON

Parses input strictly as RFC 8259 JSON and reports the first syntax error with line, column, offset, JSON Pointer and an excerpt; messages name the usual mistakes (trailing commas, single quotes, unquoted keys, comments, NaN, leading zeros) and say how to fix them. Invalid JSON is a successful response with valid: false, so check valid. For valid JSON it returns the document re-indented or minified, optionally with keys sorted, plus statistics. Only whitespace (and, with sort_keys, member order) changes: strings and numbers are copied exactly as written, so 1.0, 1e5 and 20-digit integers survive. Duplicate keys, which JSON.parse silently collapses, are listed with JSON Pointers; the output keeps the last value at the first position, as JSON.parse does. Nesting deeper than 500 levels is rejected.

Browser version (runs locally): JSON Format & Validate.

Parameters

Also accepted on every endpoint: format (json | text). Parameters may come from the query string, a JSON object body, an urlencoded or multipart form, or (for input) a text/plain body.

Response 200 application/json

Text output (format=text, text/plain): The formatted JSON, or for invalid input one line: invalid: line L, column C: message.

Errors

Errors are JSON: {"error": "<message>", "code": "<code>", "param": "<name>"?}.

Behaviour

• Idempotent: the same arguments always return the same result.
• Requires a client ID and secret (authentication). Each call is recorded as one metadata row against your client ID; inputs and outputs are never stored or logged. Responses carry cache-control: no-store.
• CORS: any origin may call this endpoint from a browser, using your credentials.

Examples

Responses below were produced by running each request through this code at build time. Long strings are shortened.

curl -X POST 'https://util.caruana.me/api/json/format' \
  -H 'content-type: application/json' \
  -d '{"input":"{\"b\":[1,2,{\"d\":1.0,\"c\":null}],\"a\":\"x\"}","sort_keys":true}'

{
  "valid": true,
  "error": null,
  "type": "object",
  "output": "{\n  \"a\": \"x\",\n  \"b\": [\n    1,\n    2,\n    {\n      \"c\": null,\n      \"d\": 1.0\n    }\n  ]\n}",
  "duplicateKeys": [],
  "warnings": [],
  "stats": {
    "depth": 3,
    "objects": 2,
    "arrays": 1,
    "members": 4,
    "strings": 1,
    "numbers": 3,
    "booleans": 0,
    "nulls": 1,
    "inputBytes": 38,
    "outputBytes": 86
  }
}

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "json_format",
    "arguments": {
      "input": "{\"b\":[1,2,{\"d\":1.0,\"c\":null}],\"a\":\"x\"}",
      "sort_keys": true
    }
  }
}

curl -X POST 'https://util.caruana.me/api/json/format' \
  -H 'content-type: application/json' \
  -d '{"input":"{\n  \"a\": 1,\n  \"b\": [true, false]\n}","indent":"none"}'

{
  "valid": true,
  "error": null,
  "type": "object",
  "output": "{\"a\":1,\"b\":[true,false]}",
  "duplicateKeys": [],
  "warnings": [],
  "stats": {
    "depth": 2,
    "objects": 1,
    "arrays": 1,
    "members": 2,
    "strings": 0,
    "numbers": 1,
    "booleans": 2,
    "nulls": 0,
    "inputBytes": 34,
    "outputBytes": 24
  }
}

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "json_format",
    "arguments": {
      "input": "{\n  \"a\": 1,\n  \"b\": [true, false]\n}",
      "indent": "none"
    }
  }
}

curl -X POST 'https://util.caruana.me/api/json/format' \
  -H 'content-type: application/json' \
  -d '{"input":"{\n  \"name\": \"demo\",\n  \"tags\": [\"a\", \"b\",]\n}"}'

{
  "valid": false,
  "error": {
    "message": "Trailing comma before \"]\": JSON does not allow a comma after the last element. Remove it.",
    "pointer": "/tags",
    "line": 3,
    "column": 21,
    "offset": 40,
    "excerpt": "  \"tags\": [\"a\", \"b\",]\n                    ^"
  },
  "type": null,
  "output": null,
  "duplicateKeys": [],
  "warnings": [],
  "stats": null
}

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "json_format",
    "arguments": {
      "input": "{\n  \"name\": \"demo\",\n  \"tags\": [\"a\", \"b\",]\n}"
    }
  }
}

curl -X POST 'https://util.caruana.me/api/json/format' \
  -H 'content-type: application/json' \
  -d '{"input":"{\"id\": 12345678901234567890, \"id\": 2}"}'

{
  "valid": true,
  "error": null,
  "type": "object",
  "output": "{\n  \"id\": 2\n}",
  "duplicateKeys": [
    {
      "key": "id",
      "pointer": "/id",
      "line": 1,
      "column": 30,
      "offset": 29,
      "firstLine": 1,
      "firstColumn": 2
    }
  ],
  "warnings": [
    {
      "message": "Integer 12345678901234567890 is beyond ±(2^53 − 1); parsers that use IEEE 754 doubles (JavaScript, many others) read it … (68 more characters)",
      "pointer": "/id",
      "line": 1,
      "column": 8,
      "offset": 7
    }
  ],
  "stats": {
    "depth": 1,
    "objects": 1,
    "arrays": 0,
    "members": 2,
    "strings": 0,
    "numbers": 2,
    "booleans": 0,
    "nulls": 0,
    "inputBytes": 37,
    "outputBytes": 13
  }
}

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "json_format",
    "arguments": {
      "input": "{\"id\": 12345678901234567890, \"id\": 2}"
    }
  }
}