JSON Schema Generator Free Online Tool 2026

Last updated March 22, 2026

Example: Nested Object Schema

// Input JSON:
{
  "user": {
    "id": 1,
    "name": "Alice",
    "address": {
      "street": "123 Main St",
      "city": "New York",
      "zip": "10001",
      "country": "US"
    }
  }
}

// Generated Schema:
{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "type": "object",
  "properties": {
    "user": {
      "type": "object",
      "properties": {
        "id":   { "type": "integer" },
        "name": { "type": "string" },
        "address": {
          "type": "object",
          "properties": {
            "street":  { "type": "string" },
            "city":    { "type": "string" },
            "zip":     { "type": "string", "pattern": "^\\d{5}$" },
            "country": { "type": "string", "minLength": 2, "maxLength": 2 }
          },
          "required": ["street", "city", "zip", "country"]
        }
      },
      "required": ["id", "name", "address"]
    }
  },
  "required": ["user"]
}

Example: Array of Objects Schema

// Input JSON:
[
  { "id": 1, "name": "Widget A", "price": 9.99,  "inStock": true  },
  { "id": 2, "name": "Widget B", "price": 14.99, "inStock": false },
  { "id": 3, "name": "Widget C", "price": 4.99,  "inStock": true  }
]

// Generated Schema:
{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "type": "array",
  "items": {
    "type": "object",
    "properties": {
      "id":      { "type": "integer" },
      "name":    { "type": "string" },
      "price":   { "type": "number", "minimum": 0 },
      "inStock": { "type": "boolean" }
    },
    "required": ["id", "name", "price", "inStock"]
  }
}

Example: Schema with Enum Detection

// Input JSON (multiple samples analyzed):
[
  { "status": "pending",   "priority": "low" },
  { "status": "active",    "priority": "medium" },
  { "status": "completed", "priority": "high" },
  { "status": "cancelled", "priority": "low" }
]

// Generated Schema (enum values inferred):
{
  "type": "array",
  "items": {
    "type": "object",
    "properties": {
      "status": {
        "type": "string",
        "enum": ["pending", "active", "completed", "cancelled"]
      },
      "priority": {
        "type": "string",
        "enum": ["low", "medium", "high"]
      }
    },
    "required": ["status", "priority"]
  }
}

Example: OpenAPI Schema Component

// Input JSON (API response):
{
  "id": 1,
  "username": "alice",
  "email": "alice@example.com",
  "createdAt": "2024-01-15T14:30:00Z",
  "updatedAt": "2024-03-10T09:15:00Z"
}

// Generated Schema (OpenAPI 3.0 compatible):
{
  "User": {
    "type": "object",
    "properties": {
      "id": {
        "type": "integer",
        "description": "Unique identifier"
      },
      "username": {
        "type": "string",
        "description": "User's login name"
      },
      "email": {
        "type": "string",
        "format": "email",
        "description": "User's email address"
      },
      "createdAt": {
        "type": "string",
        "format": "date-time",
        "description": "Account creation timestamp"
      },
      "updatedAt": {
        "type": "string",
        "format": "date-time",
        "description": "Last update timestamp"
      }
    },
    "required": ["id", "username", "email"]
  }
}

Example: Schema with $defs (Reusable Types)

// Input JSON:
{
  "order": {
    "id": "ORD-001",
    "customer": { "id": 1, "name": "Alice", "email": "alice@example.com" },
    "items": [
      { "product": { "id": 10, "name": "Widget", "price": 9.99 }, "qty": 2 }
    ],
    "shippingAddress": { "city": "New York", "zip": "10001" }
  }
}

// Generated Schema (with reusable $defs):
{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "$defs": {
    "Customer": {
      "type": "object",
      "properties": {
        "id":    { "type": "integer" },
        "name":  { "type": "string" },
        "email": { "type": "string", "format": "email" }
      },
      "required": ["id", "name", "email"]
    },
    "Product": {
      "type": "object",
      "properties": {
        "id":    { "type": "integer" },
        "name":  { "type": "string" },
        "price": { "type": "number", "minimum": 0 }
      },
      "required": ["id", "name", "price"]
    }
  },
  "type": "object",
  "properties": {
    "order": {
      "type": "object",
      "properties": {
        "id":       { "type": "string" },
        "customer": { "$ref": "#/$defs/Customer" },
        "items": {
          "type": "array",
          "items": {
            "type": "object",
            "properties": {
              "product": { "$ref": "#/$defs/Product" },
              "qty":     { "type": "integer", "minimum": 1 }
            }
          }
        }
      }
    }
  }
}

Generated TypeScript Interface

// From the same User JSON, generate TypeScript:
interface User {
  id: number;
  username: string;
  email: string;
  createdAt: string;  // ISO 8601 date-time
  updatedAt?: string; // optional
}

Paste your sample JSON to generate a JSON Schema automatically. Refine the generated schema by adding descriptions, constraints, and enum values to make it a complete API contract.

// Input JSON:
{
  "id": 42,
  "name": "Alice Smith",
  "email": "alice@example.com",
  "age": 30,
  "active": true,
  "score": 98.5,
  "notes": null
}

// Generated JSON Schema (Draft 7):
{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "type": "object",
  "properties": {
    "id":     { "type": "integer" },
    "name":   { "type": "string" },
    "email":  { "type": "string", "format": "email" },
    "age":    { "type": "integer", "minimum": 0 },
    "active": { "type": "boolean" },
    "score":  { "type": "number" },
    "notes":  { "type": ["string", "null"] }
  },
  "required": ["id", "name", "email", "age", "active"]
}