Generate TypeScript Types from API

---
description: Auto-generate type-safe API client from OpenAPI/Swagger spec
---

1. **Get Your API Schema**:
- Most APIs expose OpenAPI spec at /swagger.json or /openapi.json.
- Download it or use the URL directly.

2. **Install openapi-typescript**:
- Best tool for generating types.
// turbo
- Run npm install --save-dev openapi-typescript

3. **Generate Types**:
- Create types from schema URL.
// turbo
- Run npx openapi-typescript https://api.example.com/openapi.json -o src/types/api.ts

4. **Use Generated Types**:
- Import and use in your API calls.

import type { paths } from './types/api';
   
   type UserResponse = paths['/users']['get']['responses']['200']['content']['application/json'];
   
   async function getUsers(): Promise<UserResponse> {
     const res = await fetch('/api/users');
     return res.json();
   }

5. **Auto-Regenerate on Change**:
- Add script to package.json.

{
     "scripts": {
       "generate:types": "openapi-typescript https://api.example.com/openapi.json -o src/types/api.ts"
     }
   }

6. **Alternative: tRPC**:
- For Next.js apps, use tRPC for end-to-end type safety.
// turbo
- Run npm install @trpc/server @trpc/client @trpc/react-query @trpc/next

7. **Pro Tips**:
- Run npm run generate:types before starting development.
- Commit generated types to git for team consistency.
- Use openapi-fetch for a fully typed fetch wrapper.