JSON Schema to TypeScript

What Is JSON Schema and Why Convert It to TypeScript?

JSON Schema is the industry-standard format for describing the structure and validation rules of JSON data. It is used extensively in OpenAPI and Swagger API definitions, form validation libraries like AJV and Zod, database configuration schemas, and event-driven architectures. However, JSON Schema is a runtime validation format and does not provide compile-time type safety.

TypeScript interfaces and type aliases fill that gap. By converting your JSON Schema into TypeScript types, you gain IntelliSense autocomplete in VS Code, compile-time error detection, and self-documenting code without writing the type declarations manually. This tool performs that conversion entirely in your browser using a recursive AST (Abstract Syntax Tree) compiler.

JSON Schema Draft Support

This converter handles the core constructs shared across JSON Schema Draft-04, Draft-07, and Draft 2020-12. The following type mappings are fully supported:

• "type": "string" maps to TypeScript string
• "type": "integer" or "number" maps to TypeScript number
• "type": "boolean" maps to TypeScript boolean
• "type": "null" maps to TypeScript null
• "type": ["string", "null"] maps to TypeScript string | null (union)
• "enum": ["a", "b"] maps to TypeScript "a" | "b" (literal union)
• "anyOf" and "oneOf" map to TypeScript union types with |
• "type": "array" with "items" maps to TypeScript ItemType[]
• Nested "type": "object" is extracted into separate named interfaces

JSDoc Comments From Schema Descriptions

When your JSON Schema properties include a description field, this converter automatically promotes it to a JSDoc block comment directly above the TypeScript property. This means editors like VS Code will display the documentation on hover, making your generated types completely self-describing:

• Schema: "userId": { "type": "integer", "description": "Unique user identifier" }
• Output: /** Unique user identifier */ userId: number;

interface vs type: Which Should You Use?

TypeScript supports both interface and type for describing object shapes. The key differences: interface supports declaration merging (you can extend it later in the same file), while type is more flexible and supports union and intersection types directly. For generated API types that you do not expect to extend, either is appropriate. The converter supports both via the formatting toggle.

Known Limitation: Schema References

JSON Schema reference pointers (the "$ref" keyword, e.g., "$ref": "#/definitions/Address") enable reusable schema components. This converter does not yet resolve reference pointers, so fields using them will output as any. To work around this, inline the referenced definition into the property before converting. Full reference resolution is planned for a future version.

Privacy-First Local Processing

This JSON Schema to TypeScript converter runs entirely inside your browser memory. Because API schemas often contain proprietary data structures, security definitions, and customer field representations, uploading them to remote servers creates a confidentiality risk. Our compiler operates 100% locally. You can verify by checking the Browser DevTools Network tab and confirming zero outbound requests are made during conversion.