SCHEMA

JSON Schema Generator

Turn any JSON sample into a ready-to-use JSON Schema with types, formats, and required fields.

JSON input

Everything is parsed locally in your browser.

Sample JSON

Accepts up to 200000 characters.

JSON Schema draft

Controls the $schema keyword written at the root.

Inference options

Detect string formats

Adds format only when every sampled string matches, such as email or uuid.

Required from present keys

Marks a key required only when it appears in every merged object.

Forbid extra properties

Writes additionalProperties: false on every object.

Include examples

Adds an examples array with the first value seen for each scalar.

Infer enum

Turns repeated strings into an enum when there are 10 distinct values or fewer.

Generated schema

The schema updates as you type.

2020-12Root type: objectProperties: 21Formats: 6

{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "type": "object",
  "properties": {
    "id": {
      "type": "string",
      "format": "uuid"
    },
    "name": {
      "type": "string"
    },
    "email": {
      "type": "string",
      "format": "email"
    },
    "active": {
      "type": "boolean"
    },
    "loginCount": {
      "type": "integer"
    },
    "deletedAt": {
      "type": "null"
    },
    "createdAt": {
      "type": "string",
      "format": "date-time"
    },
    "website": {
      "type": "string",
      "format": "uri"
    },
    "tags": {
      "type": "array",
      "items": {
        "type": "string"
      }
    },
    "ratings": {
      "type": "array",
      "items": {
        "anyOf": [
          {
            "type": "number"
          },
          {
            "type": "null"
          }
        ]
      }
    },
    "profile": {
      "type": "object",
      "properties": {
        "birthDate": {
          "type": "string",
          "format": "date"
        },
        "timezone": {
          "type": "string"
        },
        "lastIp": {
          "type": "string",
          "format": "ipv4"
        }
      },
      "required": [
        "birthDate",
        "timezone",
        "lastIp"
      ]
    },
    "orders": {
      "type": "array",
      "items": {
        "type": "object",
        "properties": {
          "sku": {
            "type": "string"
          },
          "quantity": {
            "type": "integer"
          },
          "status": {
            "type": "string"
          },
          "total": {
            "type": "number"
          },
          "note": {
            "type": "string"
          }
        },
        "required": [
          "sku",
          "quantity",
          "status",
          "total"
        ]
      }
    },
    "labels": {
      "type": "array",
      "items": {}
    }
  },
  "required": [
    "id",
    "name",
    "email",
    "active",
    "loginCount",
    "deletedAt",
    "createdAt",
    "website",
    "tags",
    "ratings",
    "profile",
    "orders",
    "labels"
  ]
}

What

JSON Schema Generator definition

JSON Schema is a vocabulary that describes the shape of JSON data so it can be validated automatically. This generator reads a sample payload and infers types, required keys, string formats, and nested structures for Draft 2020-12 or draft-07.

Cases

Use Cases

Bootstrap request and response validation for a REST API.

Document the payload shape of a third-party webhook.

Generate OpenAPI component schemas from real sample data.

Add contract tests that catch breaking changes in a response.

Validate configuration files in CI before a deploy runs.

Define strict argument schemas for LLM tool calls.

How To

How to generate a JSON Schema

Paste a representative JSON sample, tune the inference options, and copy the schema.

Paste JSON

Paste a sample payload that represents the real structure into the input area.

Pick a draft

Choose Draft 2020-12 or draft-07 so the $schema keyword matches your validator.

Tune inference

Toggle format detection, required keys, additionalProperties, examples, and enum.

Copy the schema

Copy the result into your validator, OpenAPI document, or test suite.

Knowledge

Understanding JSON Schema inference

How merging works

The generator walks the parsed value, merges every array element and every repeated object into a single node, and then writes types, properties, and required lists from what it observed.

Formats and enum

String formats such as date-time, email, uuid, ipv4, and ipv6 are applied only when all samples match. Enum inference is opt-in because a small sample easily misses valid values.

Review before you validate

A generated schema is a starting point, not a contract: it can over-constrain optional fields and miss values your sample never contained. Keys such as __proto__ are emitted as ordinary properties, so keep validating untrusted payloads with a hardened validator and explicit size limits.

FAQ

What is the difference between Draft 2020-12 and draft-07?

They differ mainly in how arrays and references are described. This tool emits output that works in both and only switches the $schema value.

How are arrays with mixed types handled?

Every element is merged into one schema. When the element types differ, the tool emits anyOf with one branch per type.

When is a number typed as integer?

Only when every sampled value is a whole number. A single decimal anywhere in the sample widens the type to number.

Can I trust the generated required list?

It reflects only the sample you provided. Review it before shipping, because optional keys missing from your sample will still be marked required.

Why did my string not get a format?

A format is applied only when every sampled string at that path matches it, so one non-matching value removes it.

Is my JSON sent anywhere?

No. Parsing and schema generation run entirely in your browser, so payloads never leave your device.

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