Test-Json

Tests whether a string is a valid JSON document

Syntax

Test-Json
    [-Json] <String>
    [<CommonParameters>]
Test-Json
    [-Json] <String>
    [[-Schema] <String>]
    [<CommonParameters>]
Test-Json
    [-Json] <String>
    [-SchemaFile <String>]
    [<CommonParameters>]

Description

The Test-Json cmdlet tests whether a string is a valid JavaScript Object Notation (JSON) document and can optionally verify that JSON document against a provided schema.

The verified string can then be used with the ConvertFrom-Json cmdlet convert a JSON-formatted string to a JSON object, which is easily managed in PowerShell or sent to another program or web service that access JSON input.

Many web sites use JSON instead of XML to serialize data for communication between servers and web-based apps.

This cmdlet was introduced in PowerShell 6.1

Examples

Example 1: Test if an object is valid JSON

This example tests whether the input string is a valid JSON document.

"{'name': 'Ashley', 'age': 25}" | Test-Json

True

Example 2: Test an object against a provided schema

This example takes a string containing a JSON schema and compares it to an input string.

$schema = @'
{
  "definitions": {},
  "$schema": "http://json-schema.org/draft-07/schema#",
  "$id": "http://example.com/root.json",
  "type": "object",
  "title": "The Root Schema",
  "required": [
    "name",
    "age"
  ],
  "properties": {
    "name": {
      "$id": "#/properties/name",
      "type": "string",
      "title": "The Name Schema",
      "default": "",
      "examples": [
        "Ashley"
      ],
      "pattern": "^(.*)$"
    },
    "age": {
      "$id": "#/properties/age",
      "type": "integer",
      "title": "The Age Schema",
      "default": 0,
      "examples": [
        25
      ]
    }
  }
}
'@
"{'name': 'Ashley', 'age': '25'}" | Test-Json -Schema $schema

Test-Json : IntegerExpected: #/age
At line:1 char:37
+ "{'name': 'Ashley', 'age': '25'}" | Test-Json -Schema $schema
+                                     ~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo          : InvalidData: (:) [Test-Json], Exception
+ FullyQualifiedErrorId : InvalidJsonAgainstSchema,Microsoft.PowerShell.Commands.TestJsonCommand
False

In this example, we get an error because the schema expects an integer for age but the JSON input we tested uses a string value instead.

For more information, see JSON Schema.

Example 3: Test an object against a schema from file

JSON schema can reference definitions using $ref keyword. The $ref can resolve to a URI that references another file. The SchemaFile parameter accepts literal path to the JSON schema file and allows JSON files to be validated against such schemas.

In this example we have schema.json file which references definitions.json.

PS> Get-Content schema.json

{
  "description":"A person",
  "type":"object",
  "properties":{
    "name":{
      "$ref":"definitions.json#/definitions/name"
    },
    "hobbies":{
      "$ref":"definitions.json#/definitions/hobbies"
    }
  }
}

PS> Get-Content definitions.json

{
  "definitions":{
    "name":{
      "type":"string"
    },
    "hobbies":{
      "type":"array",
      "items":{
        "type":"string"
      }
    }
  }
}

'{"name": "James", "hobbies": [".NET", "Blogging"]}' | Test-Json -SchemaFile 'schema.json'

True

For more information, see Structuring a complex schema.

Parameters

-Json

Specifies the JSON string to test for validity. Enter a variable that contains the string, or type a command or expression that gets the string. You can also pipe a string to Test-Json.

The Json parameter is required.

Type:String
Position:1
Default value:None
Accept pipeline input:True
Accept wildcard characters:False
-Schema

Specifies a Schema to validate the JSON input against. If passed Test-Json will validate that the Json input conforms to the spec specified by the Schema parameter and return $True only if the input conforms to the provided Schema.

For more information, see JSON Schema.

Type:String
Position:2
Default value:None
Accept pipeline input:False
Accept wildcard characters:False
-SchemaFile

Specifies a schema file used to validate the JSON input. When used, the Test-Json returns $True only if the JSON input conforms to the Schema defined in the file specified by the SchemaFile parameter.

For more information, see JSON Schema.

Type:String
Position:Named
Default value:None
Accept pipeline input:False
Accept wildcard characters:False

Inputs

String

You can pipe a JSON string to Test-Json.

Outputs

Boolean

Notes

The Test-Json cmdlet is implemented by using the NJsonSchema Class.

Since PowerShell 6, PowerShell uses the Newtonsoft.Json assemblies for all JSON functions. Newtonsoft's implementation includes several extensions to the JSON standard, such as support for comments and use of single quotes. For a full list of features, see the Newtonsoft documentation at https://www.newtonsoft.com/json.