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JSON Schema Validator

JSON Schema Validator

Validate a JSON document against a JSON Schema (draft-07 + formats) — live, in your browser.

Try a sample:

JSON Schema

JSON Instance

    Examples

    Validate a user object against a schema

    Input
    Schema: {
  "type": "object",
  "required": ["name", "email"],
  "properties": {
    "name": { "type": "string", "minLength": 1 },
    "email": { "type": "string", "format": "email" },
    "age": { "type": "integer", "minimum": 0 }
  }
}
Document: {
  "name": "",
  "email": "not-an-email"
}
    Output
    2 validation errors:
/name — must NOT have fewer than 1 characters (minLength)
/email — must match format "email" (format)
Expected: string
Got: "not-an-email"

    Both errors are reported with their instance paths. The allErrors flag means both failures appear, not just the first one.

    Validate an array with item constraints

    Input
    Schema: {
  "type": "array",
  "items": { "type": "number" },
  "minItems": 1
}
Document: ["a", "b", "c"]
    Output
    /0 — must be number (type)
Expected: number
Got: "a"

    Each non-number item is flagged with its array index as the instance path (/0, /1, /2).

    About this tool

    JSON Schema is a vocabulary that describes the expected structure of a JSON document — which properties must be present, what types they must have, and what constraints they must satisfy. It is the standard way to validate API request and response bodies, configuration files, and any JSON data that must conform to a contract before being processed.

    This validator uses Ajv (Another JSON Schema Validator) with draft-07 support, format validation (email, uri, date-time, and more), strict:false mode (to allow additional keywords without errors), and allErrors mode (which reports every violation, not just the first one). The output shows each error with its JSON pointer instance path and a human-readable message.

    How to use

    1. Paste the JSON Schema

      Paste the schema that defines the expected structure into the Schema panel. It is validated first so you can confirm the schema itself is well-formed.

    2. Paste the JSON document

      Drop the document you want to validate into the Document panel. Each property that violates the schema is reported with its path and a message.

    3. Read the error list

      Every validation error is shown with its instance path (e.g. /user/email) and the specific rule that failed. Fix the document and re-validate until all errors clear.

    Use cases

    Validating API request bodies

    Define a JSON Schema for your API payload and validate incoming requests before processing them, catching missing fields and type errors early.

    Testing configuration files

    Write a schema for your app's config.json and validate it at startup to fail fast with a clear error instead of silent wrong values.

    Contract testing between services

    Both the producer and consumer of an API can validate against the same JSON Schema, ensuring the contract is honoured without a full integration test.

    Common mistakes

    Mistake:Using format validation without knowing Ajv's defaults.

    Fix:Ajv validates formats by default only when the ajv-formats package is loaded. This tool ships with formats enabled (email, uri, date-time, etc.), but if your schema relies on a format not in that set, it will not be validated.

    Mistake:Expecting the validator to coerce types.

    Fix:Draft-07 does not coerce types by default. A string '42' will not pass an integer schema. Use type: ['string', 'integer'] if the field can accept both.

    Mistake:Forgetting required fields in nested objects.

    Fix:The required array lists only top-level properties by default. For nested objects, add required inside the nested object's subschema or use JSON Path conditions.

    Frequently asked questions

    Related guides

    Validating JSON Against a Schema: A Practical Guide to JSON Schema

    What JSON Schema guarantees, how draft-07 works, and how instance paths identify fields that are missing, malformed, or the wrong type.

    References & standards

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