TypeScript Academy · Lesson

OpenAPI Codegen: Auto-Generated Types

Generate TypeScript types from OpenAPI specs.

Lesson 3 of 413 steps

OpenAPI Codegen: Auto-Generated Types is a free TypeScript Academy lesson on CoddyKit. This is lesson 3 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the TypeScript Academy learning path, and your progress syncs across the web and the CoddyKit app. The TypeScript Academy course includes 4 lessons in total.

Welcome

OpenAPI codegen generates TypeScript types and client code from API specifications, eliminating manual type maintenance.

Why Codegen

Manually writing types for large APIs is error-prone and out of sync. Codegen derives types from the single source of truth: the OpenAPI spec.

openapi-typescript

openapi-typescript generates TypeScript types from an OpenAPI spec file.

npm install -D openapi-typescript
npx openapi-typescript ./api.yaml -o ./src/types/api.ts

Generated Types

The tool generates path, operation, and schema types.

import type { paths } from './types/api';
type GetUserResponse = paths['/users/{id}']['get']['responses']['200']['content']['application/json'];

openapi-fetch Client

Use openapi-fetch with the generated types for a fully typed client.

import createClient from 'openapi-fetch';
const client = createClient<paths>({ baseUrl: 'https://api.example.com' });
const { data, error } = await client.GET('/users/{id}', { params: { path: { id: 1 } } });

Swagger Codegen

Swagger Codegen generates full client SDKs in TypeScript.

npm install @openapitools/openapi-generator-cli -g
openapi-generator-cli generate -i api.yaml -g typescript-axios -o ./src/client

orval

orval generates React Query hooks and Zod schemas from OpenAPI specs.

npm install -D orval
orval --input api.yaml --output src/api

Keeping Types in Sync

Run codegen in CI to detect drift between the spec and generated types.

Schema-First API Development

Define the OpenAPI spec first, generate types and client code, then implement the server.

MSW with Generated Types

Use Mock Service Worker with generated types for type-safe API mocking in tests.

Type-Safe URL Construction

Generated clients enforce correct path parameters and query string shapes.

Quick Check

What is the primary benefit of using OpenAPI TypeScript codegen?

Answer it in the interactive lesson

Recap

OpenAPI Codegen: Auto-Generated Types: mastered the key concepts and patterns.

Free to start

Learn TypeScript with an AI tutor — free

Write and run real code in your browser, get instant help from a 24/7 AI tutor, and pick up where you left off on the web or in the app.

Courses: 101
Lessons: 352

Start learning free View the full course

Frequently Asked Questions

Is the “OpenAPI Codegen: Auto-Generated Types” lesson free?

Yes — the full text of “OpenAPI Codegen: Auto-Generated Types” is free to read here on the web. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the TypeScript Academy course, upgrade to CoddyKit PRO. The TypeScript Academy course includes 4 lessons in total.

What will I learn in “OpenAPI Codegen: Auto-Generated Types”?

Generate TypeScript types from OpenAPI specs. You practise TypeScript Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.

Do I need any experience to start TypeScript Academy?

No prior experience is required. TypeScript Academy on CoddyKit is structured for beginners through advanced learners, so you can start here or from the beginning and move at your own pace. This is lesson 3 of 4.

How long does the “OpenAPI Codegen: Auto-Generated Types” lesson take?

Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.

Can I write and run code in this TypeScript Academy lesson?

Yes. Every TypeScript Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.

All lessons in this course

Typing Fetch Responses with Generic Wrappers
Runtime Validation with Zod
OpenAPI Codegen: Auto-Generated Types
Type-Safe tRPC Client Overview

← Back to TypeScript Academy