JSON Schema Validator

The validator checks a JSON document against a JSON Schema and tells you whether it conforms — and if not, exactly what is wrong and where. Each problem names the place in the data, such as tags[1] or (root), what is wrong with it in plain words, and the rule in the schema that it broke. It understands draft-04, draft-07 (which also covers draft-06), 2019-09 and 2020-12, and picks the right one from the schema’s $schema line. Use it to check an API response against its contract, a config file against its schema, or a schema you are writing against the examples it is meant to accept.

1. Paste the schema on the left and the data to check on the right, or press “Try an example” to see a document with five problems.
2. Read the result below. Valid data says so; invalid data lists each problem with its path, message and schema rule.
3. If the schema has no $schema line, 2020-12 rules are used. Choose another draft from the Draft menu when you know the schema was written for one.
4. Edit either side and the result updates.

• $ref works within the schema you paste, including $defs and definitions. A $ref to a URL is not fetched; paste the referenced definitions into $defs instead. The error message says which reference could not be resolved.
• Formats are checked: date, time, date-time, duration, email, hostname, ipv4, ipv6, uri, uri-reference, uri-template, url, uuid, regex, json-pointer and relative-json-pointer. The 2020-12 standard makes format checks optional; most validators apply them, and this one does.
• When a value breaks a rule deep inside a schema, only the most specific failure is listed — “tags[1] should be a string” rather than the same failure repeated at tags and at the root.
• Each side can be up to 5 MB.
• This checks data against a schema. It does not check that a schema is itself well written, beyond whether it can be used.
• The schema and the data are checked in your browser. Nothing is uploaded, and the tool never fetches anything — including schemas referred to by URL.

Leave it on “From $schema”. A schema that starts with a $schema line says which draft it uses. If yours has none and was written for an older tool, draft-07 is the most common choice.

The schema sets additionalProperties to false, so any property it does not list is rejected. Either the data has a misspelt or extra field, or the schema is missing a property it should allow.

It follows the same JSON Schema standards but uses a different library, one that interprets the schema directly rather than generating code — which is what lets it run inside this site’s security policy. On unusual schemas the two can word their errors differently.

Yes, if you paste the component’s schema itself. OpenAPI 3.1 schemas are 2020-12 JSON Schema; OpenAPI 3.0 uses a close variant that draft-04 or draft-07 handles for most schemas.