Validate JSON data against JSON Schema definitions with detailed error reporting and schema generation.
JSON Schema Validator compares a JSON instance with a separate JSON Schema and reports where the instance violates declared constraints such as types, required properties, numeric ranges, string patterns, or array rules. It can also generate a starting schema from sample JSON. The common surprise is that valid JSON is not necessarily schema-valid JSON: successful parsing only confirms the text follows JSON syntax. Also, listing a name under `properties` does not make that property mandatory; the schema must include it in `required`.
Supply the JSON document to test and the schema that describes its permitted shape. The validator parses both documents, evaluates applicable schema keywords, and reports failed constraints with their associated locations. A successful result means that particular instance satisfies that schema. It does not establish that the instance meets requirements that the schema never expressed.
Schema generation derives a candidate definition from the structure and value types present in sample JSON. Review the result before treating it as a contract. One sample cannot reveal every permitted alternative, optional property, range, pattern, or conditional relationship. Generated constraints may therefore be narrower or less complete than the intended data model.
The `properties` keyword supplies subschemas for properties when they occur; it does not require those names to occur. Add the property name to the containing object's `required` array when omission should fail validation. Conversely, `required` does not by itself define the property's allowed type or value, so the two keywords commonly appear together.
Usually no. Generation can describe observations from the supplied sample, but it cannot infer unstated intent. Review optional versus required fields, additional properties, nullability, arrays, formats, ranges, alternatives, and reusable definitions. Validate several deliberately valid and invalid examples before publishing the result as a contract.
The behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.
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