JSON Schema Validator Online

What this tool does

A JSON Schema is a JSON document that describes what other JSON must look like. The validator reads the draft from the schema's $schema, or from the Draft menu when there is none, resolves $ref to $defs, definitions, $anchor and $id inside the schema, and checks every keyword. It collects all errors instead of stopping at the first (up to 100). Each error has an instance path, a JSON Pointer to the value in your data; a schema path, the location of the keyword that failed; and a message such as must have required property 'id'. When anyOf or oneOf fails, the result also lists why each option failed. Problems in the schema itself, such as an invalid regex, an unknown type name or a $ref to another file, are reported separately, because they mean part of the data could not be checked. Formats are checked by default; turn Check formats off to treat format as an annotation, which is what the 2019-09 and 2020-12 specifications do unless a validator is told otherwise. If either pane is not valid JSON, you get the line and column of the syntax error first.

Example input and output

Schema:
{
  "type": "object",
  "required": ["id", "email"],
  "properties": {
    "id": { "type": "integer" },
    "email": { "type": "string", "format": "email" }
  }
}

Data:
{ "id": "42", "name": "Ada" }

✗ 2 errors
(root)  must have required property 'email'
  required · #/required
/id  must be an integer (got string)
  type · #/properties/id/type

Schema:
{
  "type": "array",
  "items": { "$ref": "#/$defs/user" },
  "$defs": {
    "user": {
      "type": "object",
      "required": ["id"],
      "properties": {
        "id": { "type": "integer", "minimum": 1 },
        "role": { "enum": ["admin", "editor", "viewer"] }
      },
      "additionalProperties": false
    }
  }
}

Data:
[
  { "id": 1, "role": "admin" },
  { "id": 0, "role": "owner", "nickname": "bo" }
]

✗ 3 errors
/1/id  must be >= 1
  minimum · #/$defs/user/properties/id/minimum
/1/role  must be one of: "admin", "editor", "viewer"
  enum · #/$defs/user/properties/role/enum
/1/nickname  property 'nickname' is not allowed (additionalProperties is false)
  additionalProperties · #/$defs/user/additionalProperties

Schema:
{
  "$defs": {
    "base": { "properties": { "id": { "type": "integer" } } }
  },
  "allOf": [{ "$ref": "#/$defs/base" }],
  "properties": { "name": { "type": "string" } },
  "unevaluatedProperties": false
}

Data:
{ "id": 1, "name": "Ada", "admin": true }

✗ 1 error
/admin  property 'admin' is not allowed (unevaluatedProperties is false)
  unevaluatedProperties · #/unevaluatedProperties

Common errors and fixes

"int" is not a JSON Schema type; use "integer"

The seven types are string, number, integer, boolean, object, array and null. Names from programming languages such as int, float, bool or dict are not types, and neither is date: use "type": "string" with "format": "date".

"required" is inside "properties", so it declares a property called "required"

Move "required": ["id", "email"] up one level so it sits next to "properties". The older "required": true on a single property is draft-03 syntax and is ignored by every current draft.

property 'name' is not allowed (additionalProperties is false), although allOf declares it

additionalProperties only counts properties declared in the same schema object, not in allOf, anyOf or a $ref. Use "unevaluatedProperties": false at the top level (2019-09 and later), or repeat the properties next to additionalProperties.

A pattern accepts values you meant to reject

pattern is not anchored: "[0-9]{5}" matches ABC12345XYZ because it contains five digits. Add ^ and $, as in "^[0-9]{5}$", to match the whole string.

"prefixItems" is not part of draft-07 and is ignored

The schema is written for a different draft than the one being used. Set "$schema" to the draft you write: 2020-12 replaced the items array with prefixItems and additionalItems with items, and in draft-07 every keyword next to a $ref is ignored.

$ref "https://example.com/address.json" points outside this schema

DevPrix never fetches other files or URLs, so that part of the data is not checked. Copy the referenced schema into "$defs" and change the reference to "#/$defs/address".

must match format "email", but another validator accepted the same data

Many validators treat format as an annotation unless you enable it: Ajv needs the ajv-formats plugin and Python's jsonschema needs a FormatChecker. Turn off Check formats to see what an annotation-only validator would report.

Common use cases

• Checking an API request or response body against the schema it is supposed to follow
• Finding out why a payload fails schema validation in CI, an API gateway or a form library
• Writing and testing a schema for a JSON config file before you publish it
• Generating a starter schema from sample JSON and tightening it rule by rule
• Checking test fixtures and seed data against the schema they must match

Privacy and security notes

• The schema and the data are validated by JavaScript in this browser tab. Nothing is uploaded, and no network requests are made: even a $ref to a URL is reported instead of fetched.
• Share copies a link that carries the JSON data after the # in the URL. Browsers do not send that part to servers, but anyone you give the link to can read it, so do not share links that contain secrets.
• Before pasting production data into any online tool, remove access tokens, passwords and personal data you do not need.

Frequently asked questions