JSON Schema Validator

Paste a JSON Schema and a JSON document to validate them against each other. All errors are shown with the field path, error message, and failing keyword. Uses AJV with Draft-07 support.

Common schema keywords

The most-used JSON Schema Draft-07 keywords

Keyword	Description
`type`	Constrain the value type: "string", "number", "integer", "boolean", "array", "object", "null".
`required`	Array of property names that must be present in the object.
`properties`	Define the schema for each named property. Properties not listed are allowed by default.
`additionalProperties`	Set to false to reject any properties not listed in 'properties'. Set to a schema to constrain them.
`enum`	Value must be one of the listed values exactly.
`minimum / maximum`	Numeric range constraints (inclusive). Use exclusiveMinimum / exclusiveMaximum for strict bounds.
`minLength / maxLength`	String length constraints.
`pattern`	String must match this regex (ECMA 262 syntax).
`items`	Schema that every element of an array must satisfy.
`minItems / maxItems`	Array length constraints.
`$ref`	Reference another schema definition. Use with $defs or definitions for reusable sub-schemas.

Common use cases

API contract validation

Define a schema for request/response bodies and validate incoming data before processing. Catch missing fields and wrong types at the boundary.

Config file validation

Validate JSON configuration files (package.json, tsconfig.json, .eslintrc) against a schema before the application loads them.

CI pipeline data checks

Add a validation step to your CI pipeline to ensure data exports, fixtures, or seed files match the expected schema before they're deployed.

Webhook payload testing

Paste a webhook payload and your expected schema to verify the structure matches before writing integration code.

Frequently asked questions

What is JSON Schema?

JSON Schema is a vocabulary for describing and validating the structure of JSON documents. A schema defines the expected types, required fields, value ranges, and formats. It's used for API request/response validation, configuration file validation, and data contract enforcement.

Which JSON Schema draft does this support?

This tool uses AJV (Another JSON Validator) with Draft-07 support. Draft-07 is the most widely adopted version and covers all common use cases. Draft 2019-09 and Draft 2020-12 introduced new keywords (unevaluatedProperties, $vocabulary) that are not supported here.

What does additionalProperties: false do?

It rejects any JSON object that contains a property not listed in the 'properties' keyword. Without it, JSON Schema allows extra properties by default. Use additionalProperties: false when you want a strict contract — any unexpected field will fail validation.

How do I validate an array of objects?

Use type: "array" at the top level with an items keyword pointing to the object schema: { "type": "array", "items": { "type": "object", "properties": { ... } } }. Every element in the array will be validated against the items schema.

What is the difference between minimum and exclusiveMinimum?

minimum: 0 allows 0 and any larger number. exclusiveMinimum: 0 allows any number strictly greater than 0 — 0 itself fails. In Draft-07, exclusiveMinimum is a number. In older drafts it was a boolean paired with minimum.

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