OpenAPI 3.x to TypeScript types in browser

OpenAPI 3.x is the current standard for describing REST APIs. It introduced components/schemas (replacing Swagger 2.0's definitions), requestBody for typed request payloads, and a richer content map on responses. OpenAPI 3.1 further aligns with JSON Schema draft 2020-12, adding support for const, prefixItems, and dropping the non-standard nullable flag in favour of type: [string, null].

The OpenAPI to TypeScript browser generator handles all three subversions (3.0.0 through 3.1.x). It detects the spec version from the openapi field and applies version-aware parsing — for example, recognising both nullable: true (3.0.x) and type: ["string", "null"] (3.1) as producing string | null in the output.

OpenAPI 3.x features in the generated types

• paths interface: every route and method with typed parameters (path, query, header), requestBody, and responses
• components.schemas interface: all named schemas resolved from #/components/schemas/ refs
• $ref resolution: local refs resolved to components["schemas"]["Name"] TypeScript index access
• Composition: allOf → intersection (&), anyOf/oneOf → union (|)
• Nullable: nullable: true and type: [T, "null"] both produce T | null

How to use

1. Go to OpenAPI to TypeScript Types, paste your OpenAPI 3.x spec (JSON or YAML), and click Generate TypeScript.
2. Review the generated types in the preview panel. Schemas map to named interfaces under components.schemas; path operations map to paths entries.
3. Download types.d.ts and import it into your project alongside openapi-fetch or any typed HTTP client.

Related tools

• OpenAPI to TypeScript Types — main generator
• Swagger 2.0 to TypeScript — legacy API support
• OpenAPI to React Query types
• Generate from OpenAPI YAML
• YAML Validator — verify your spec before converting