JSON Schema Validation

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Practical JSON Schema examples for required fields, types, enums, arrays, nested objects, and validation workflows.

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## Schema basics

Basic object schema

↗#

{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "type": "object",
  "properties": {
    "name": { "type": "string" },
    "active": { "type": "boolean" }
  },
  "required": ["name", "active"],
  "additionalProperties": false
}

# Require a string name and boolean active flag.

Enum restriction

↗#

{
  "type": "object",
  "properties": {
    "status": {
      "type": "string",
      "enum": ["draft", "published", "archived"]
    }
  },
  "required": ["status"]
}

# Restrict a value to a known set of strings.

Array item validation

↗#

{
  "type": "array",
  "items": {
    "type": "object",
    "properties": {
      "id": { "type": "integer" },
      "email": { "type": "string", "format": "email" }
    },
    "required": ["id", "email"]
  }
}

# Validate every item in an array.

## Schema validation workflows

Validate with Ajv CLI

↗#

npx ajv-cli validate -s schema.json -d data.json

# Validate a JSON file against a schema file.

Validate multiple files with Ajv

↗#

npx ajv-cli validate -s schema.json -d 'fixtures/*.json'

# Validate a whole set of JSON documents.

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