OpenAPI to TypeScript
LiveGenerate TypeScript interfaces and types from OpenAPI specifications.
Understanding TypeScript
OpenAPI (formerly Swagger) specifications define REST API contracts — endpoints, request/response schemas, authentication, and error formats — in a machine-readable YAML or JSON document. Generating TypeScript types from OpenAPI specs ensures frontend applications have type-safe API clients that match the backend contract. When the OpenAPI spec changes, regenerated types catch breaking changes at compile time, preventing runtime errors from schema mismatches.
Paste your OpenAPI 3.0 specification (YAML or JSON) and generate TypeScript interfaces for all schemas, request bodies, and response types. Supports nested objects, arrays, enums, oneOf/anyOf/allOf combinators, nullable types, and $ref references. Output clean, ready-to-use TypeScript code.
The Devkitr OpenAPI to TypeScript Converter generates TypeScript interfaces, request/response types, and API client functions from OpenAPI 3.0/3.1 specifications. Paste an OpenAPI spec to get TypeScript types for all schemas, path parameters, query parameters, and response bodies.
In a typical development workflow, OpenAPI to TypeScript becomes valuable whenever you need to generate typescript interfaces and types from openapi specifications. Whether you are working on a personal side project, maintaining production applications for a company, or collaborating with a distributed team across time zones, having a reliable browser-based conversion tool eliminates the need to install desktop software, write one-off scripts, or send data to third-party services that may log or retain your information. Since OpenAPI to TypeScript processes everything locally on your device, your data stays private and your workflow stays uninterrupted — open a browser tab, paste your input, get your result.
Key Features
Schema to Interface
Converts OpenAPI component schemas into TypeScript interfaces with proper types for all properties, including $ref resolution.
Path Type Generation
Creates typed request parameter interfaces and response types for each API endpoint path and HTTP method.
Enum Generation
Converts OpenAPI enum schemas to TypeScript string literal unions or const enums based on your preference.
Discriminated Unions
Maps OpenAPI oneOf/anyOf schemas to TypeScript discriminated union types with proper type narrowing support.
How to Use OpenAPI to TypeScript
Paste OpenAPI Spec
Enter your OpenAPI 3.0/3.1 specification in YAML or JSON format.
Select Output Options
Choose between interface/type alias, enum style, and whether to generate API client functions.
Review Generated Types
Check schema types, endpoint parameter types, response types, and enum definitions for accuracy.
Copy TypeScript Code
Copy the generated types into your frontend project for a type-safe API client implementation.
Use Cases
Frontend API Client
Generate typed fetch/axios wrapper functions from the OpenAPI spec for a fully type-safe frontend API layer.
SDK Generation
Create TypeScript SDK types for your API that consumers can import for type-safe API integration.
Contract Testing
Use generated types to validate test mocks against the OpenAPI schema at compile time.
Code Review Automation
Regenerate types on spec changes and review TypeScript compiler errors to identify breaking API changes.
Pro Tips
Regenerate types automatically in your CI/CD pipeline whenever the OpenAPI spec changes to catch breaking changes early.
Use discriminated unions for response types that vary by status code — 200 OK responses and 400 error responses have different shapes.
Prefer string literal unions over TypeScript enums for OpenAPI enums — they are more ergonomic and match JSON string values.
Add the OpenAPI spec version to generated file headers so developers know which API version the types correspond to.
Common Pitfalls
Manually writing types instead of generating from the spec
Fix: Manual types drift from the spec over time. Always generate from the OpenAPI spec to ensure types match the actual API contract.
Not handling nullable schemas correctly
Fix: OpenAPI nullable: true should generate Type | null in TypeScript. Missing null handling causes runtime crashes on null responses.
Generating types once and never updating them
Fix: Add type generation to your build pipeline (pre-build script or CI step). Stale types create a false sense of type safety.
Frequently Asked Questions
QWhich OpenAPI versions are supported?
OpenAPI 3.0.x is fully supported. Swagger 2.0 specs are partially supported with basic type generation.
QDoes it generate API client code?
This tool focuses on type generation (interfaces). It does not generate fetch/axios client code.
QHow are nullable types handled?
Properties with nullable: true generate TypeScript union types with null (e.g., string | null).
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