Online JSON Schema Validator [2025]

JSON Schema is a vocabulary that allows you to annotate and validate JSON documents. It describes the structure of your JSON data, specifying data types, required fields, value constraints (like minimum/maximum), patterns, and more. Think of it like a blueprint or a contract for your JSON data.

It's widely used for validating API request/response bodies, configuration files, and ensuring data consistency across different systems or components. JSON Schema itself is written in JSON.

• •

  Ensure Data Quality & Consistency:

  Guarantee that incoming or outgoing JSON data adheres to the expected format, preventing errors caused by incorrect types, missing fields, or invalid values.

• •

  API Contract Enforcement:

  Validate client requests and server responses against a defined schema to ensure both sides adhere to the API contract.

• •

  Automated Testing:

  Use JSON Schema validation as part of your automated tests to verify the structure of data generated by your application.

• •

  Documentation & Clarity:

  The schema itself serves as clear documentation for the expected JSON structure.

Validation against a schema can fail for many reasons beyond basic JSON syntax errors, including:

• Incorrect data type (e.g., providing a string where a number is expected: `"price": "10.99"`).
• Missing required properties (e.g., omitting `"productId"` if it's listed in the schema's `required` array).
• Value constraints not met (e.g., a number below a `minimum`, a string not matching a `pattern`).
• Array errors (e.g., fewer items than `minItems`, more than `maxItems`, non-unique items if `uniqueItems` is true).
• Additional properties present when `additionalProperties: false` is set in the schema.
• Enum mismatch (value provided is not one of the allowed values in the schema's `enum` array).

This validator uses the Ajv library to provide detailed error messages, including the path within the JSON data where the error occurred.