JSON Schema Generator Guide

Generate JSON Schema automatically from your existing JSON data. Perfect for API documentation, data validation, and type checking.

What is JSON Schema?

JSON Schema is a vocabulary that allows you to annotate and validate JSON documents. It describes:

• Data types
• Required fields
• Value constraints
• Default values
• Data structure

Why Use JSON Schema?

1. Data Validation

Automatically validate incoming data:

{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "type": "object",
  "properties": {
    "name": {"type": "string"},
    "age": {"type": "number", "minimum": 0}
  },
  "required": ["name", "age"]
}

2. API Documentation

Auto-generate API docs from schemas

3. Type Safety

Generate TypeScript interfaces from schemas

4. Contract Testing

Ensure APIs return correct data structures

How Our Generator Works

Input JSON

{
  "name": "John Doe",
  "age": 30,
  "email": "john@example.com",
  "hobbies": ["reading", "gaming"],
  "address": {
    "city": "New York",
    "zip": "10001"
  }
}

Generated Schema

{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "type": "object",
  "properties": {
    "name": {
      "type": "string"
    },
    "age": {
      "type": "number"
    },
    "email": {
      "type": "string",
      "format": "email"
    },
    "hobbies": {
      "type": "array",
      "items": {
        "type": "string"
      }
    },
    "address": {
      "type": "object",
      "properties": {
        "city": {"type": "string"},
        "zip": {"type": "string"}
      },
      "required": ["city", "zip"]
    }
  },
  "required": ["name", "age", "email", "hobbies", "address"]
}

Using the Generator

1. Paste your JSON data
2. Generate schema instantly
3. Customize constraints and requirements
4. Export schema for use

Try it: JSON Schema Generator

Schema Features

Data Types

{
  "string": {"type": "string"},
  "number": {"type": "number"},
  "integer": {"type": "integer"},
  "boolean": {"type": "boolean"},
  "null": {"type": "null"},
  "array": {"type": "array"},
  "object": {"type": "object"}
}

String Constraints

{
  "type": "string",
  "minLength": 1,
  "maxLength": 100,
  "pattern": "^[A-Za-z]+$",
  "format": "email"
}

Number Constraints

{
  "type": "number",
  "minimum": 0,
  "maximum": 100,
  "multipleOf": 5
}

Array Constraints

{
  "type": "array",
  "items": {"type": "string"},
  "minItems": 1,
  "maxItems": 10,
  "uniqueItems": true
}

Validation Examples

JavaScript (using Ajv)

const Ajv = require('ajv');
const ajv = new Ajv();

const schema = {
  type: "object",
  properties: {
    name: {type: "string"},
    age: {type: "number", minimum: 0}
  },
  required: ["name", "age"]
};

const validate = ajv.compile(schema);
const valid = validate({name: "John", age: 30});

if (!valid) {
  console.log(validate.errors);
}

Python (using jsonschema)

import jsonschema

schema = {
    "type": "object",
    "properties": {
        "name": {"type": "string"},
        "age": {"type": "number", "minimum": 0}
    },
    "required": ["name", "age"]
}

data = {"name": "John", "age": 30}
jsonschema.validate(instance=data, schema=schema)

Advanced Features

Conditional Validation

{
  "if": {
    "properties": {"country": {"const": "USA"}}
  },
  "then": {
    "properties": {"zip": {"pattern": "^\\d{5}$"}}
  }
}

Enum Values

{
  "type": "string",
  "enum": ["red", "green", "blue"]
}

Definitions and References

{
  "definitions": {
    "address": {
      "type": "object",
      "properties": {
        "street": {"type": "string"},
        "city": {"type": "string"}
      }
    }
  },
  "properties": {
    "home": {"$ref": "#/definitions/address"},
    "work": {"$ref": "#/definitions/address"}
  }
}

Best Practices

1. Start with Examples

Generate schema from real data samples

2. Add Constraints

Refine generated schema with validation rules

3. Document Your Schema

Add descriptions:

{
  "type": "string",
  "description": "User's full name",
  "examples": ["John Doe", "Jane Smith"]
}

4. Version Your Schemas

Track schema changes over time

5. Test Thoroughly

Validate with various data samples

Common Use Cases

1. API Validation

Validate request/response bodies

2. Configuration Files

Validate app configuration

3. Form Validation

Client-side form validation

4. Data Migration

Ensure data integrity during migration

5. Documentation

Auto-generate API documentation

Tools Integration

OpenAPI/Swagger

Use schemas in API specifications

TypeScript

Generate interfaces:

interface User {
  name: string;
  age: number;
  email?: string;
}

GraphQL

Convert schemas to GraphQL types

Schema Versions

• Draft-04: Older, widely supported
• Draft-07: Recommended, good balance
• Draft-2019-09: Latest features
• Draft-2020-12: Most recent

Our generator supports all versions!

Conclusion

JSON Schema is essential for API development and data validation. Use our Schema Generator to create schemas instantly from your JSON data!