Generate JSON Schema Automatically
Writing JSON Schema by hand is one of those tasks that sounds simple until you actually do it. The syntax is verbose, nested objects need their own schema definitions, and getting the required array right is fiddly. This tool infers it all from your actual data — paste a JSON sample, get a complete schema.
The generated schema follows the Draft-07 specification, which is the most widely supported version. Types are inferred from values — strings, numbers (integer vs float), booleans, arrays, and nested objects all get the right type. Non-null fields are automatically added to the required array.
What is JSON Schema?
JSON Schema is a vocabulary for describing the structure of JSON documents. Think of it like TypeScript types but for JSON data — it defines what fields should exist, what types they should be, whether they're required, and structural rules like minimum/maximum values, string patterns, and array lengths.
Validation with AJV
The most popular JSON Schema validator in JavaScript is AJV (Another JSON Validator). Use the generated schema with AJV to validate API request bodies, configuration files, or any JSON data. AJV compiles schemas into optimized validation functions, so it's fast enough for request-per-request validation in production.
API Documentation
JSON Schema is used by OpenAPI (Swagger) to describe API request and response bodies. Generate schemas from actual API responses, refine them with constraints, and add them to your OpenAPI spec. Tools like SwaggerUI use these schemas to generate interactive documentation and API testing interfaces.
From Schema to Code
JSON Schema is the starting point for many code generation pipelines. Tools likequicktype generate typed classes from JSON Schema in multiple languages. Our tool goes the other direction — from data to schema — giving you the foundation for a fully typed pipeline: Data → JSON Schema → TypeScript/Python/Java classes.
Schema Refinement
The auto-generated schema captures structure and types, but you'll want to add constraints for production use. Things like minimum/maximumfor numbers, pattern for string formats (email, URL, date), enumfor fixed value sets, and additionalProperties: false to reject unknown fields. The generated base gives you the structure — you add the business rules.
Related JSON Tools
Validate data against the generated schema with our JSON Schema Validator. Need runtime validation too? Generate Zod schemas for TypeScript or Joi schemas for Node.js.