JSON Schema Generator

Generate JSON Schema (Draft 2020-12) from sample data instantly in your browser

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How to generate JSON Schema from sample data

jsonsql.dev generates JSON Schema (Draft 2020-12) instantly in your browser. No data is sent to any server — your JSON stays on your machine.

Paste sample JSON — paste a JSON object or array that represents your data structure into the input editor on the left.

Click Generate Schema — the tool analyzes your JSON structure, infers types, detects string formats (email, URI, date, UUID), and produces a complete JSON Schema.

Copy or download — click Copy to copy the schema to your clipboard, or Download to save it as a .json file.

Example

Input:

{
  "id": "550e8400-e29b-41d4-a716-446655440000",
  "name": "Alice Johnson",
  "email": "[email protected]",
  "age": 30,
  "active": true,
  "website": "https://alice.dev",
  "created": "2026-01-15T10:30:00Z",
  "tags": ["developer", "writer"]
}

Generated schema (Draft 2020-12):

{
  "$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" },
    "age": { "type": "integer" },
    "active": { "type": "boolean" },
    "website": { "type": "string", "format": "uri" },
    "created": { "type": "string", "format": "date-time" },
    "tags": {
      "type": "array",
      "items": { "type": "string" }
    }
  },
  "required": ["id", "name", "email", "age", "active", "website", "created", "tags"]
}

Features

Generates JSON Schema Draft 2020-12 from any sample JSON data
Infers types: string, number, integer, boolean, null, object, array
Detects string formats: email, URI, date, date-time, IPv4, UUID
Handles nested objects recursively with full property schemas
Handles arrays by merging item schemas from all elements
Supports mixed types with oneOf
Detects required fields from array items (present in all objects)
Optional: include examples from sample data
Optional: include auto-generated descriptions
Copy schema or download as .json file
Dark and light theme support
Works offline — 100% client-side, no data uploads

JSON Schema Generator vs other tools

Feature	jsonsql.dev	jsonschema.net	quicktype.io
Browser-based	Yes	Yes	Yes
Client-side only	Yes	No (server)	No (server)
Draft 2020-12	Yes	Yes	Draft-06
Format detection	Yes (6 formats)	Yes	Limited
Mixed type support	Yes (oneOf)	Yes	Yes
Include examples	Yes (toggle)	Yes	No
Download schema	Yes	Yes	Yes
Dark mode	Yes	No	No
No sign-up	Yes	Free tier	Yes

Understanding JSON Schema Draft 2020-12

JSON Schema is a vocabulary for annotating and validating JSON documents. Draft 2020-12 is the latest stable version, replacing Draft 2019-09. Key improvements include the $dynamicRef keyword and simplified prefixItems for tuple validation.

A JSON Schema describes the shape of your data — property names, types, required fields, string formats, array item types, and more. Schemas are used for API validation, form generation, documentation, and code generation.

Frequently asked questions

What JSON Schema draft version does this tool generate?

This tool generates JSON Schema Draft 2020-12, the latest stable version of the JSON Schema specification. The output includes the $schema keyword pointing to the official 2020-12 meta-schema.

Does it detect string formats like email and date?

Yes. The generator detects 6 string formats automatically: email, URI, date (YYYY-MM-DD), date-time (ISO 8601), IPv4 addresses, and UUIDs. Detected formats are added as the "format" keyword in the schema.

How does it handle arrays with mixed types?

When an array contains elements of different types, the generator creates a oneOf schema listing each unique type. For example, an array with strings and numbers produces items: { oneOf: [{ type: "string" }, { type: "number" }] }.

How are required fields determined?

By default, all properties found in an object are marked as required. For arrays of objects, the tool detects which keys appear in every item and marks only those as required. You can also toggle "All required" to force all fields as required.

Can I include examples in the generated schema?

Yes. Enable the "Examples" toggle in the toolbar to include example values from your sample data in the generated schema. This is useful for API documentation and OpenAPI specs.

What is the difference between number and integer types?

The generator distinguishes between integer (whole numbers like 42) and number (decimals like 3.14). In JSON Schema, integer is a subtype of number — an integer value also validates against a number schema, but not vice versa.