JSON Schema is a vocabulary that allows you to annotate and validate JSON documents. It defines the structure, data types, required fields, and constraints for JSON data. For example, a schema can specify that an API response must include a "name" field (string, required) and an "age" field (integer, minimum 0). JSON Schema follows the specification at json-schema.org.

Which JSON Schema versions are supported?

Most validators support JSON Schema Draft 7 (2019), Draft 6 (2017), and Draft 4 (2013). Draft 7 is the most widely adopted. Some tools also support Draft 2019-09 and Draft 2020-12. Check the validator documentation for specific version support. Draft 7 is recommended for new projects due to broad compatibility.

What happens if validation fails?

The validator returns detailed error messages indicating which fields failed validation and why. For example: "property \"age\" must be >= 0" or "required property \"email\" is missing". Error messages include JSON paths (e.g., /users/0/age) pointing to the exact location of violations, making debugging straightforward.

Can I auto-generate a schema from JSON data?

Yes. Many validators include schema generation features that analyze sample JSON and create a corresponding schema. However, auto-generated schemas are starting points. They infer types from examples but cannot detect business rules (e.g., email format, age ranges). Always review and enhance auto-generated schemas with custom validation rules.

How do I validate nested objects and arrays?

JSON Schema supports nested validation using the "properties" keyword for objects and "items" keyword for arrays. You can define schemas for nested structures at any depth. For example, a user object with an address object inside validates both levels. Array validation can specify that all items must conform to a specific schema or allow mixed types.

Can JSON Schema validate API responses?

Yes. JSON Schema is widely used for API contract validation. Define schemas for request/response payloads, then validate actual API data against those schemas in tests or production. This catches breaking changes early. Tools like Postman, Swagger/OpenAPI, and API testing frameworks integrate JSON Schema validation natively.

JSON Schema Validator - Validate JSON Online

How to Validate JSON Schema

Paste your JSON schema into the schema panel
Paste your JSON data into the data panel
Click validate to check compliance
Review validation results with detailed error messages

Why Use Our JSON Schema Validator?

Draft Support: Compatible with JSON Schema Draft 7 and newer
Detailed Errors: Pinpoint exactly which properties fail validation
Schema Validation: Validates both your schema and your data
Auto-Generate Schemas: Create schemas from example JSON
Examples Included: Preloaded templates to get started quickly
100% Free: No registration or usage limits

What is JSON Schema?

JSON Schema is a vocabulary for annotating and validating JSON documents. It defines the expected structure, data types, required properties, and constraints for JSON data. Think of it as a contract that your JSON must follow.

Example: A user schema might require email (string), age (number, minimum 0), and optional address (object). If you try to validate JSON with age: -5 or email: 123, the validator will reject it. This ensures data quality and prevents bugs from malformed input.

Use cases: API contract testing to ensure endpoints return expected structures, validating user input before saving to databases, ensuring data quality in data pipelines, and documenting API schemas for developer onboarding. JSON Schema is widely used in OpenAPI/Swagger specifications.

Privacy & Security

Your JSON data and schemas are validated entirely in your browser. No data is uploaded to servers, stored, or logged. The validation happens locally using JavaScript, keeping your data private.