JSON Schema Validator

Keywords this validator checks

It checks type, including lists such as ["string", "null"], plus enum, const, required, properties, patternProperties, additionalProperties, items, minimum, maximum, minLength, maxLength, pattern, minItems, maxItems, allOf, anyOf, and oneOf. A $ref is followed when it points inside the same schema, such as #/definitions/address or #/$defs/address. Other keywords, such as exclusiveMinimum, multipleOf, uniqueItems, and if/then, are ignored, as are references to other files; for those, use a full implementation such as Ajv for JavaScript or jsonschema for Python.

format is checked for email, date, date-time, uri, uuid, and ipv4, and any other format passes. These are shape tests: email wants name@domain.tld, date rejects impossible days such as 2026-02-30, date-time needs a time zone such as Z or +02:00, and uri needs a scheme, so a relative path like /docs fails.

Schema mistakes that let bad data through

Listing a field under properties does not make it required; it must also appear in the required array, or a record without it passes. A pattern is not anchored, so [0-9]{5} accepts abc123456; write ^[0-9]{5}$ to match the whole value. And integer rejects 3.5 while number accepts it. To start from a sample instead of a blank page, generate a schema with JSON to JSON Schema and tighten it.

How to use it

1. Paste JSON data on the left and JSON Schema definition on the right.
2. Click Validate JSON Payload.
3. Review property error paths, data type mismatches, and required field violations.

Privacy & limitations

Validation runs strictly in local client JavaScript memory.