JSON Schema Validator

What it does

JSON Schema is a vocabulary for describing the shape of JSON data: which properties an object must have, what type each value is, allowed ranges and patterns, array lengths and much more. APIs use it in OpenAPI specifications, editors use it for autocomplete in configuration files, and back ends use it to reject bad requests.

This validator checks a JSON document against a schema and lists every problem it finds. Each error shows where it is in the data (a JSON Pointer such as /tags/1), a readable message, and the schema keyword that failed, so you can fix the data or the schema quickly. It supports draft 2020-12, 2019-09, draft-07 and draft-04, including $ref, $defs, allOf/anyOf/oneOf, if/then/else, unevaluatedProperties and format checks.

How to use

1. Paste the data into JSON data and the schema into JSON Schema, or upload a file to each side. Sample loads a user record with a few deliberate mistakes.
2. The result updates as you type: a green badge when the data is valid, otherwise the number of errors and a list of them.
3. Leave Draft on Auto to follow $schema, or force a version. Turn off Report all errors to stop at the first failure.
4. Copy errors copies the list as plain text, for a bug report or a code review.

If either side is not valid JSON, the message says whether the data or the schema is broken and gives the line and column.

Example

With this schema:

{
  "type": "object",
  "required": ["id"],
  "properties": {
    "id": { "type": "integer" },
    "age": { "type": "integer", "minimum": 0 }
  }
}

the document {"age": -1} produces two errors: at (root), the required property id is missing; at /age, the value is below the minimum of 0.

Tips

Add "additionalProperties": false to catch misspelled property names, which otherwise pass silently. Use enum or const for fixed values, and pattern for strings such as product codes. When a schema grows, move repeated parts into $defs and reference them with $ref.