✓ JSON Schema Validator
Paste a JSON Schema and some JSON data, and see every place the data fails the schema — with a JSON-pointer path to exactly where.
This covers a practical subset of JSON Schema Draft-07, hand-rolled with no external library:
type, required, properties,
items, enum, minimum/maximum,
minLength/maxLength, pattern, and
additionalProperties: false. Not supported (silently ignored if present):
$ref, oneOf/anyOf/allOf/not,
if/then/else, const,
multipleOf, exclusiveMinimum/exclusiveMaximum,
minItems/maxItems/uniqueItems,
minProperties/maxProperties, patternProperties,
propertyNames, contains, format, and schema composition/definitions in general.
Full Draft-07 is a large spec — this is meant for everyday "does this JSON roughly match this shape" checks, not spec-complete conformance testing.