A subset of draft 2020-12: type, enum, const, required, properties, additionalProperties, items, length and numeric bounds, pattern, a few formats, anyOf, oneOf, allOf, not, if/then/else, and local $ref.

Why did a valid-looking schema fail?

Keywords such as patternProperties, contains, and unevaluatedProperties are named in the errors and are not applied.

Are schema patterns safe to run?

Patterns longer than 80 characters, nested quantifiers, and strings over 5,000 characters are refused instead of being executed.

JSON Schema Validator

Check instance data against a schema object. The validator covers common assertions and local $ref pointers, and it tells you when a keyword is outside that subset.

Checks a subset of JSON Schema draft 2020-12. Unsupported keywords are listed and the document is not treated as valid.

JSON data

JSON Schema

Validation

Valid for the supported subset.

No errors.

How to use it

Paste the instance data and the schema. Both must be JSON.
Validate. Errors name a path and the assertion that failed.
Remove or replace unsupported keywords if the tool lists them.

Common mistakes

Unknown keywords do not pass silently. The result stays invalid until they are removed.
format checks for email, date-time, uri, and uuid are light pattern checks.
$ref only resolves #/$defs/name and #/definitions/name.

Examples

Required number

{ "type": "object", "required": ["id"], "properties": { "id": { "type": "number" } }, "additionalProperties": false }

Local reference

{ "$defs": { "id": { "type": "integer" } }, "properties": { "id": { "$ref": "#/$defs/id" } } }

Frequently asked questions

Processing stays in this browser tab. What you paste is not uploaded, and this tool does not write it to local storage.