Validate JSON against a schema
Paste a JSON Schema and a JSON document to validate. Get path-level error messages instantly.
Schema & Document
Paste your JSON Schema and the JSON document to validate.
Validation result
The document is valid against the schema.
All constraints in the schema are satisfied. The document is valid.
Why this tool exists
Vultio JSON Schema Validator checks whether a JSON document conforms to a JSON Schema definition, reporting path-level errors like $.user.age: value -5 is less than minimum 0.
It is useful for API contract testing, configuration validation, and CI checks — without requiring a backend or any npm package to be installed.
Common use cases
- Validate an API request or response body against its OpenAPI schema during development.
- Check a configuration file against a schema before committing it to a repository.
- Catch missing required fields in a JSON payload before sending it to an API.
- Test that a data migration produced valid output conforming to the target schema.
- Prototype and iterate on a JSON Schema definition without setting up a dev environment.
Example input / output
Required field missing
Input
Output
Type mismatch
Input
Output
Common errors
Schema is not valid JSON.
Cause: The schema panel contains a syntax error.
Fix: Format the schema using the JSON Formatter, fix any errors, then paste it back.
additional property "x" is not allowed
Cause: The schema sets additionalProperties: false but the document has extra fields.
Fix: Either add the field to the schema properties, or remove it from the document.
Related guides
How to write JSON Schemas, validate documents online, and use draft-07 keywords for robust API contract testing.
Standards & references
The official documentation for all JSON Schema keywords, types, validation rules, and schema composition.
The formal specification document for JSON Schema draft-07, the version supported by this validator.
Related tools
Format raw JSON to make it easier to inspect.
Convert JSON into TypeScript interfaces or Go structs.
Compare two JSON objects and highlight differences visually.
Frequently asked questions
What is JSON Schema validation?
JSON Schema is a vocabulary for describing the structure of JSON data. A validator checks whether a JSON document conforms to a schema, reporting exactly which fields fail and why.
Which JSON Schema draft is supported?
The validator supports the core keywords from JSON Schema draft-07: type, properties, required, additionalProperties, items, minLength, maxLength, minimum, maximum, pattern, enum, const, allOf, anyOf, oneOf, and not.
What does a validation error message look like?
Each error includes the JSON path to the failing value (e.g. $.user.age) and a human-readable message describing the constraint that was violated.
Can I validate arrays and nested objects?
Yes. The validator recurses through all nested objects and arrays, reporting errors at the exact path where each violation occurs.
Is my JSON sent to a server?
No. Validation runs entirely in your browser. Neither the schema nor the JSON document is uploaded or transmitted anywhere.