Open API (OAS 3.0) Typescript generator

generator, nodejs, openapi, openapi-generator, openapi3, swagger, typescript
npm install @typoas/cli@1.2.0



Typoas is an OpenAPI 3.X generator for Typescript. It's inspired by openapi-generator but is written in Typescript for Typescript. The generator uses the Typescript AST to generate code instead on relaying on templates which allows better schemas definitions and other cool stuff.

Main features are:

  • Fully typed
  • Support for allOf, oneOf and anyOf schemas.
  • References $ref handling (with cyclic refs)
  • Uses fetch api (can be customized)
  • Automatically convert format: 'date-time' to JS Date
  • Handle API Key, HTTP Config and OAuth21 auth security schemes
  • JSDoc for schemas and operations
  • And more...

1: OAuth2 scheme does not handle flows to retrieve an accessToken. You need to provide your own accessToken through the provider.getConfig() function.

The project is split into 3 parts:


It will generate a single TS file containing all the code specific to the underlying API. This file only has a single dependency on @typoas/runtime. You need to manually add @typoas/runtime to your dependencies. It handles common things like serialization/authentification


Ues the generator from the CLI

You can generate the TS client from the spec from the command line:

yarn dlx @typoas/cli generate -i my-spec.json -n MyClient -o src/client.ts
npx @typoas/cli generate -i my-spec.json -n MyClient -o src/client.ts

Here is a short list of supported command line options:

    -i, --input [path/url]         Path or URL to the OpenAPI JSON specification (yaml/json format)
    -o, --output [path]            Path where to write the generated TS file
    -n, --name                     Class name of the generated client
    --js-doc, --no-js-doc          Whether to add JS Doc to the generated code (default: true)
    --only-types                   Use it to only generate types in #components/schemas/
    --version                      Output the version number
    -h, --help                     Display help for command

or you can use it in code:

import cli from '@typoas/cli';

await cli.run(
    stdin: process.stdin,
    stdout: process.stdout,
    stderr: process.stderr,

Use the generator from the API

The API is still at an alpha stage, so it may break between minors.

It uses typescript API to generate usable code:

import { readFileSync, writeFileSync } from 'fs';
import { createPrinter, NewLineKind, SourceFile } from 'typescript';
import { generateClient, getStringFromSourceFile } from '@typoas/generator';

const specs = JSON.parse(readFileSync('path/to/github-openapi.json', 'utf8'));
const src = generateClient(specs, 'GithubClient');
const data = getStringFromSourceFile(src);

writeFileSync('./src/client.ts', data, 'utf8');

Use the generated code

Once the file is generated you'll be able to use it like this:

import fetch from 'node-fetch';
import { ServerConfiguration } from '@typoas/runtime';
import { GithubClient } from './client';

// Inject fetch polyfill into NodeJS env.
if (!globalThis.fetch) {
  // @ts-ignore
  globalThis.fetch = fetch;

const client = new GithubClient(
  new ServerConfiguration('https://api.github.com', {}),

    repo: 'typoas',
    owner: 'embraser01',
  .then((list) => console.log('List of PRs', list))
  .catch((err) => console.error('Error while getting PRs', err));


You can find examples in the examples folder.


Pull requests are welcome. For major changes, please open an issue first to discuss what you would like to change.