JSON Schema is a vocabulary for annotating and validating JSON documents. It describes the structure, types, and constraints of your JSON so tools and APIs can validate data automatically. Draft 7 and OpenAPI-style schemas are widely supported.

How do I generate a JSON Schema from sample JSON?

Paste your sample JSON into the generator at unblockdevs.com/json-schema-generation. The tool infers types (string, number, boolean, array, object) and required fields, then outputs a Draft 7 or OpenAPI-compatible schema you can edit or use in validation.

Is the generated schema free to use?

Yes. The JSON Schema Generator is free with no signup. All processing runs in your browser — your data is never sent to any server. Copy and use the schema in any project, API, or validation tool.

Can I use the schema with OpenAPI or AJV?

Yes. The generator outputs schemas compatible with OpenAPI 3.0 and AJV (the most popular JavaScript JSON Schema validator). Use the schema in your OpenAPI spec or pass it directly to AJV to validate request and response bodies.

Does the generator handle nested objects and arrays?

Yes. The generator recursively analyzes all levels of nesting to produce a complete schema including nested object properties, array item schemas, and inferred formats like email and URI.

How do I validate JSON against a schema?

In JavaScript use AJV: const ajv = new Ajv(); const validate = ajv.compile(schema); const valid = validate(data). In Python use jsonschema: jsonschema.validate(instance=data, schema=schema). This tool also includes a built-in validator — paste your JSON and schema to test instantly.

How do I use $ref in JSON Schema?

$ref allows you to reference and reuse schema definitions. Define reusable schemas under $defs (Draft 2020-12) or definitions (Draft 7), then reference them with $ref: "#/$defs/MyType". This keeps large schemas DRY and maintainable.

How do I generate a JSON Schema from sample data?

Paste one or more representative JSON examples into this generator. The tool infers types, required fields, and common formats automatically. For best results, include samples that cover all possible field values — for example, both null and non-null values if a field is nullable.

All tools

JSON Schema Generator — Auto-Generate from Sample JSON

Paste any JSON and instantly generate a Draft 7 or OpenAPI schema. Built-in validator included. 100% client-side.

100% in-browserNo signupFree forever

JSON Schema Generator

Generate JSON Schema from sample JSON. Supports Draft 7 and OpenAPI formats. Validate JSON against schemas.

Sample JSON

Schema Format

Learn More About JSON Schema

JSON Schema Generator Tutorial: Create Schemas from JSON

Complete tutorial on generating JSON Schema from sample JSON. Learn how to create schemas, validate JSON, use Draft 7 and OpenAPI formats.

Read Guide →

JSON Schema Generator and Validation: Complete Guide

Comprehensive guide to JSON Schema generation and validation with examples and best practices.

Read Guide →

What Is JSON Schema?

JSON Schema is a vocabulary for annotating and validating JSON documents. A schema describes the shape of your data — which fields exist, what types they are, which are required, and what formats or constraints apply. Tools like AJV, jsonschema (Python), and OpenAPI use schemas to validate requests and responses automatically at runtime.

Writing schemas by hand is tedious and error-prone, especially for deeply nested payloads. This generator analyzes a sample JSON document and outputs a complete, accurate schema in seconds — inferring types, detecting formats like email, uri, and date-time, and marking all present fields as required by default.

How it works

Generate a Schema in Seconds

Paste your JSON

Drop a sample JSON object or array into the input panel — from an API response, config file, or data export.

Choose format

Select JSON Schema Draft 7 (widest library support) or OpenAPI Schema for use in OpenAPI specs.

Generate

Click Generate. The tool infers types, formats, and required fields to produce a complete schema instantly.

Validate & export

Test any JSON against the schema using the built-in validator, then copy or download the schema file.

Use cases

When Developers Use JSON Schema

🛡️

TypeScript Validation

Generate a schema from a sample response and use it with AJV to add runtime validation that complements your TypeScript types.

📖

API Documentation

Bootstrap OpenAPI component schemas from existing response payloads instead of writing them from scratch.

📋

Form Validation

Use the generated schema with react-hook-form, Formik, or any JSON-Schema-aware form library to validate user input.

💡

IDE Autocomplete

Add the schema to your VS Code settings to get autocomplete and inline validation for JSON config files.

🤝

Data Contracts

Share the schema with upstream or downstream teams as a machine-readable contract for what your API accepts or produces.

⚙️

Config File Validation

Validate application config files on startup against a schema to catch misconfiguration before it causes runtime errors.

FAQ

Frequently Asked Questions

1What is JSON Schema?

JSON Schema is a vocabulary for annotating and validating JSON documents. It describes the structure, types, and constraints of your data so tools can validate it automatically. Draft 7 and OpenAPI-style schemas are the most widely supported versions.

2What is the difference between JSON Schema Draft 7 and OpenAPI Schema?

Draft 7 is the standalone JSON Schema specification with full support for $ref, allOf, anyOf, and oneOf. OpenAPI Schema is a subset/superset used inside OpenAPI 3.0 specs. Choose OpenAPI if the schema goes into an OpenAPI spec; choose Draft 7 for everything else.

3Which JSON Schema validators work with the generated schema?

The generated Draft 7 schema works with AJV (JavaScript/Node.js), jsonschema (Python), Json.NET (C#), and most other major validators. The OpenAPI schema is compatible with Swagger UI, Redoc, and OpenAPI validator tools.

4Does it detect email, URI, and date formats automatically?

Yes. The generator checks string values against common formats — email, uri, date-time, and date — and adds the corresponding format keyword to the schema property automatically.

5Are all fields marked as required?

By default the generator marks every key present in the sample as required. You can edit the schema after generation to remove fields from the required array for optional properties.

6How does it handle arrays with mixed types?

If an array contains items of a single type the generator emits items: {"type": "..."}. For mixed-type arrays it uses items: {} (any type) — you can refine this manually with oneOf or anyOf.

7Is my data sent to any server?

No. All schema generation and validation happens entirely in your browser. Your JSON is never transmitted to any server, logged, or stored.

8How do I make a field required in JSON Schema?

Add the field name to the required array of the parent object schema: {"type":"object","properties":{"name":{"type":"string"}},"required":["name"]}. Fields not in required are optional by default.

9What is the additionalProperties keyword?

Set additionalProperties: false to reject undeclared keys (strict mode), true (default) to allow them, or provide a sub-schema to validate any additional keys against that schema.

10What is the difference between oneOf, anyOf, and allOf?

allOf requires validity against ALL listed schemas. anyOf requires validity against AT LEAST ONE. oneOf requires validity against EXACTLY ONE — the most restrictive, used for mutually exclusive types.

11How do I generate TypeScript types from JSON Schema?

Use json-schema-to-typescript (npm install -g json-schema-to-typescript) and run json2ts schema.json > types.ts. Quicktype is another popular option that supports many target languages from JSON Schema input.

12How do I convert a JSON Schema to a Pydantic model?

Use datamodel-code-generator (pip install datamodel-code-generator). Run: datamodel-codegen --input schema.json --output model.py. It generates Pydantic v1 or v2 models from JSON Schema or OpenAPI files.

Learn more

Developer Guides

📖JSON Schema Guide 📖JSON Best Practices 📖API Validation with Schemas 📖Fix JSON Validation Errors

Feedback for json_schema_generation

Tell us what's working, what's broken, or what you wish we built next — it directly shapes our roadmap.

You make the difference

Good feedback is gold — a rough edge you hit today could be smoother for everyone tomorrow.

Feature ideas often jump the queue when lots of you ask.
Bug reports with steps get fixed faster — paste URLs or examples if you can.
Name and email are optional; we won't use them for anything except replying if needed.

Stay Updated

Get the latest tool updates, new features, and developer tips delivered to your inbox.

What you'll get

Product updates & new tools
JSON, API & developer tips
Unsubscribe anytime — no hassle

Get in touch

Feature ideas, bugs, or a quick thanks — we read every message.

support@unblockdevs.com