JSON Schema Generator — Generate Draft-07 Schema from JSON

What is JSON Schema?

JSON Schema is a vocabulary for annotating and validating JSON documents. It defines the expected structure, types, and constraints of your data. Draft-07 is the most widely supported version, compatible with AJV, Joi, Fastify, OpenAPI 3.0, and more.

Why Generate Schemas from Sample JSON?

Writing JSON Schema by hand is tedious and error-prone. Our generator infers the schema directly from your sample payload — perfect for documenting APIs, validating incoming data, or creating OpenAPI spec components.

Schema Inference Rules

Every key becomes a property with an inferred type
All keys present in the sample are added to required
Nested objects generate nested $defs references
Arrays infer items type from the first element
Null values generate ["string", "null"] union types

Frequently Asked Questions

Which JSON Schema draft does the generator produce?

The generator outputs Draft-07 schemas, the most widely supported version compatible with AJV, Fastify, and OpenAPI 3.0.

Can I use the generated schema for API validation?

Yes. Copy the schema and use it with AJV, Joi, Zod, or any JSON Schema validator library.

How are required fields determined?

All keys present in your sample JSON are marked as required by default. Edit the schema to make specific fields optional.

JSON Schema Generator: Infer Draft-07 Schemas from Sample Data