JSON Schema Validator

Validate JSON data against a JSON Schema. Get detailed error messages with exact paths for any violations.

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JSON Data
JSON Schema

JSON Schema Best Practices

Write better schemas and catch more validation errors.

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Start with the Required Fields

Define your 'required' array first, then add type constraints for each property. This catches missing fields early and documents your data contract clearly for other developers.

2

Use Descriptive Error Messages

Add a 'description' field to each property in your schema. When validation fails, these descriptions help developers understand what data is expected without reading the full schema.

3

Leverage Schema Composition

Use allOf, anyOf, and oneOf to compose complex schemas from simpler ones. This promotes reuse and keeps your schemas DRY. Use $ref to reference shared definitions.

4

Validate in CI/CD Pipelines

Use JSON Schema validation in your build pipeline to catch invalid configuration, test fixtures, or API contract violations before deployment. This prevents runtime errors in production.

Schema Validation Features

Comprehensive JSON Schema validation tools.

Schema Draft Support

Supports JSON Schema Draft 4, 6, 7, 2019-09, and 2020-12 specifications.

Detailed Error Reports

Get precise error messages with JSON paths pointing to exactly where validation failed.

Side-by-Side View

View your JSON data and schema side by side for easy cross-referencing.

What is JSON Schema?

JSON Schema is a vocabulary that lets you validate the structure and content of JSON data. It describes the expected shape, types, and constraints of a JSON document — similar to how a database schema defines the structure of a table.

Basic Example

A schema that requires a "name" (string) and "age" (number):

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

Valid Data

{ "name": "Alice", "age": 30 }

Invalid Data

{ "name": 123, "age": -5 }

Common Keywords

type

Defines the expected type: string, number, object, array, boolean, null

required

Lists properties that must be present in an object

properties

Defines schemas for each property of an object

items

Schema for array items — validates each element

enum

Restricts value to a fixed list of allowed values

pattern

Validates a string against a regular expression pattern

JSON Schema Validator FAQ

What is JSON Schema?

JSON Schema is a vocabulary for annotating and validating JSON documents. It defines the structure, types, and constraints that your JSON data should follow.

Which schema drafts are supported?

The validator supports JSON Schema Draft 4, 6, 7, 2019-09, and 2020-12. The draft version is auto-detected from the $schema keyword.

Can I validate nested objects?

Yes, the validator fully supports nested schemas including $ref references, allOf/anyOf/oneOf combinators, and recursive schemas.

How do I specify required fields in a schema?

Add a 'required' array at the same level as 'properties' containing the names of mandatory fields. List each required property name as a string in the array, then define type constraints under 'properties' for validation.

What is the difference between anyOf, oneOf, and allOf?

allOf means the data must match ALL listed schemas. anyOf means it must match at least ONE. oneOf means it must match EXACTLY one (and fail the rest). Use allOf for combining base schemas, anyOf for flexible unions, and oneOf for strict alternatives.

Does the validator check the schema itself for errors?

Yes, the schema must be valid JSON and conform to JSON Schema syntax. If your schema has structural issues (e.g., invalid type values or malformed keywords), the validator will report schema-level errors.

Can I use $ref to reference shared definitions?

Yes, internal $ref references to definitions within the same schema document are fully supported. This lets you define reusable sub-schemas in a 'definitions' or '$defs' section and reference them throughout your schema.

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