What Is JSON Schema? Examples You Can Copy

Updated October 1, 2026

A first example

This JSON describes a user.

{
  "id": 42,
  "name": "Ada Keller",
  "email": "ada@example.com",
  "roles": ["admin"]
}

The schema for it

The schema says the document is an object, names each property and its type, and lists which properties must be present.

{
  "type": "object",
  "properties": {
    "id": { "type": "integer", "minimum": 1 },
    "name": { "type": "string", "minLength": 1 },
    "email": { "type": "string", "format": "email" },
    "roles": {
      "type": "array",
      "items": { "enum": ["admin", "editor", "viewer"] }
    }
  },
  "required": ["id", "name", "email"],
  "additionalProperties": false
}

JSON Schema GeneratorPaste JSON and get a JSON Schema for it. Built for LLM structured outputs, API validation and docs.

The keywords you will use most

type: string, number, integer, boolean, object, array or null.
properties: the fields of an object, each with its own schema.
required: the fields that must be present. Fields not listed are optional.
additionalProperties: set it to false to reject fields the schema does not name.
items: the schema every element of an array must match.
enum: a fixed list of allowed values.
minimum, maximum, minLength, maxLength, minItems, maxItems: limits on numbers, strings and arrays.
format: a hint such as email, date-time, uri or uuid.
description: a sentence for the people, and the language models, that read the schema.
$ref: a pointer to a schema defined once under $defs and reused.

Where JSON Schema is used

API validation. The server rejects a request body that does not fit, before any other code runs.
API documentation. OpenAPI describes request and response bodies with JSON Schema.
Config files. Editors such as VS Code read a schema to autocomplete and underline mistakes in files like package.json.
LLM structured outputs. You give the model a schema and the provider guarantees the answer fits it.
Test data. A generator can fill a schema with random values.

Random JSON GeneratorGenerate random sample JSON from a preset or your own JSON Schema, with a seed for repeatable data.

Which draft to use

JSON Schema has versions called drafts. Draft-07 has the widest support in validators and tools. Draft 2020-12 is the newest and is what OpenAPI 3.1 uses.

For most schemas the two look the same. The differences are in less common keywords, such as $defs replacing definitions. Pick the draft your validator supports and name it in the $schema field.

How to validate

Use a library. Ajv is the common choice in JavaScript, and jsonschema in Python. Both take a schema and a document and return a list of errors with the path of each failing field.

What is JSON Schema? Examples you can copy